Most marathons that have corrals line up their runners within the corrals right at the start line. NYC is one of the few races (along with runDisney) that pre-stages the corrals in one area and then has everyone move from that pen along a relatively brief path to get to the starting line. And in NYC's case, they have three different sets of corrals and starting lines. (London also has multiple starting lines and merges the courses, but they don't have seeded corrals like NYC, Disney, Boston, and (to an extent) Marine Corps Marathon do.) For the times that I've run NYC, it has worked quite well. And given that they not only have three different starting lines of multiple corrals, but also five separate waves, they pretty much HAVE to set it up this way, so that they can pre-stage one wave when the preceding one has been moved out to the starting line, and keep as continuous a flow as possible. NYC seems to have this system pretty well down.
Having the three distinct courses also works wonders for making sure that the roadway (both on the Verazzano-Narrows Bridge and on the early streets of Brooklyn) isn't SO overwhelmingly packed that it takes forever and a day for people to thin out enough so that you can maintain a full stride at your chosen pace and not be required to bob and weave excessively.
Crowd control: Like many of the larger marathons, NYC is hit-and-miss with respect to properly controlling the crowd. What's necessary is for the spectators to stay on the sidewalks, not crowd into the roadway, especially in the early miles and early hours when there are large volumes of runners flowing along the course. Spectators should not be obstacles, but become exactly that when they encroach on the roadway. While I was more than willing to slap lots of high-fives during NYC this time (which is not my norm), it should be because I'm close enough to the sidewalk to take advantage of the outstretched arm, not because the people on the side of the road have decided to come 10-20 feet closer in, closing off that much real estate for runners who want to move around people in front of them. Hell, while the final 2 miles inside Central Park are exciting for everyone involved, losing that much real estate makes an already narrow spot on the course that much more difficult to handle. When I was pacing the 3:40 group for MCM the previous week, I took advantage of my pacer sign on a very long stick to dramatically and overtly motion to people who had come way too far into the roadway to move back, and get the heck out of our way.
Aid Stations: To me, these were a bit of a mixed bag for NYC this year, though I suspect that may be in part because of the heat. What did NYC get right? They had explicitly clear and very prominent signs at each stretch of table indicating what was Gatorade and what was water. They also not only color-coded the cups (green branded Gatorade cups for the Gatorade, and blue/white cups for the water), but all of the volunteers maning those tables had a corresponding poncho on (helping to protect them from the inevitable splashing): green for Gatorade, and white for water. Wonderfully clear, as opposed to some races where they don't have different color cups for each liquid, nor a consistent order of which will appear first and which second (or, even worse, possibly have them intermixed multiple times along the length of tables). What did NYC do wrong, IMO? They didn't have enough tables of cups (read: not enough volunteers handing out cups). There were multiple times where I was shut out of most of the stretch of table for water (only once where I was totally shut out). This sort of thing happens at lots of marathons, but when you have 50k runners on the course, it's pretty much expected that your aid stations will be that much longer than any of your competitor races. And given the hot conditions for the race, it was all the more expected that we would have enough water (or Gatorade) to get to at any stop. There was even one aid station where they had NO ONE handing out the water. They had volunteers present, just none that were handing off to the runners, so to get any water there required a dead stop to be more sure of getting a cup lest you inadvertently knock off a slew of cups in the effort to get one.
Additionally, according to other accounts that I read from people further back in the pack, there were multiple times when the aid stations had run out of Gatorade and/or water entirely. While it sounds like NYC actually had the liquids available on-hand, they actually ran out of cups to pour them into. So, you could fill up if you were willing to stop and had your own container, but otherwise were SOL. When you have hot conditions, you should know that tons more will be taken than in more ideal conditions. While there are lots of people, like me, who carry their own water for drinking during the race, on hot days, the water from the table is used for dousing oneself and moderating core body temperature. I started doing so from the very first aid station all the way to the last, and almost every time I was using three cups of water over my head.
Along those same lines, insufficient garbage pails for runners to throw their cups into, or for volunteers to rake up the cups and throw them into, was also a problem. It was astounding just how many cups were strewn about. And given that so many runners don't seem to understand the basic etiquette of emptying out the water and crushing the cup prior to disposing of it (and, preferably, throwing it to the side of the road, if not into a garbage pail), that made the situation all the more tricky to navigate. (Thankfully it wasn't a cold, and therefore slick, day.)
Lemon-Lime. YUCK! Truly detestable stuff that I can't stomach at all. Fruit Punch or Cool Frost Gatorade, sure. But Lemon-Lime? Egads. But, clearly, it's popular enough, otherwise they would surely be using a different flavor. This is definitely one of those situations where I just have to "suck it up" that I don't like something. Given that I carry my own Clif Shot Bloks anyway, the Gatorade on course is of no consequence for me. Doesn't mean I can't gripe about it. :-)
Smoking: According to my parents, I have been against smoking since I was an infant. They both credit me with getting my dad to quit "cold turkey" when I was only a few months old because I refused to let him touch me given the stench of the cigarette smoke. My feelings towards cigar and pot smoking are even more strident; I loathe them. If people want to kill themselves with those products, go for it. But don't put that crap into the air that I *have* to breathe while running the course. If you want to smoke something while watching the marathon, watch on TV -- not by the side of the course, subjecting the people who need to breathe to something that is deliterious to one's ability to breathe. It's not just the smell - after all, there may be some bad food odors that I want to skirt away from - rather it's something that literally negatiely affects breathing that I object being subjected to. I know it's a pipe dream that something could be one about it (by this or any other city where any of these substances is legal), but a guy can dream, no?
Finish Line: NYC does about as well as can be done given that they have about 10 blocks' worth of space that they use for the post-finish collection of medals, ponchos, recovery bags, etc., but the biggest problem that most marathons suffer from -- including NYC -- is people stopping dead in their tracks right after they cross the finish line. MOVE, PEOPLE! There are other people behind you that would like to be able to cross the line and neither trip over nor body slam their way through another person. Just keep on walking. Even slowly moving forward is better than a dead stop in the middle of the roadway. The top elites (who don't have a pack immediately behind them) or back-of-the-packers that are in the part of the crowd that is so thinned out that there is no real risk of being in someone's way who has insufficient opportunity to weave/walk around you are really the only ones who can stop dead and not affect anyone else.
Having all of the post-race recovery items in a single bag (that you can put over your shoulder, even) is fabulous. This way, you can readily get to the item that you want without having to worry about juggling around all the other items. Disney is among the worst at this, despite conducting races for more than 30 years -- you can pick up heatsheet, a bottle of Gatorade, a bottle of water, a box filled with that year's goodies, and a banana, and are expected to be able to manage that prior to collecting your gear check bag (if you checked one) and getting it open.
On the flip side, one lesson that Disney learned several years ago that NYC seems not to have: tables at the backdrop photos. By the time you have collected your recovery items, medal(s), heathsheet or poncho, and gear check bag, you then have the opportunity to get your photo taken with the race backdrop. Several years ago (sometime after the Dopey Challenge started up in 2014) Disney finally started placing small tables right net to the backdrops where runners could place all of the aforementioned items down to not have in hand for the photo, and then easily retrieve the items to move off. NYC doesn't have that, so if you want a photo without any of that in your hands, you need to bend over to some extent to place the items on the ground, and then again to pick them up. This motion is setting up the runner - TWICE - for getting all the more lightheaded than they might otherwise be. Plus it may wind up straining other muscles that just want to creak and need some TLC & recovery time.
Having a working app that tracks the runners is always nice, and far too often seems to fail. As I understand it, NYC's worked this year (whereas MCM's crapped out utterly). And NYC has an additional feature beyond providing readouts for each timing mat the runner crosses during the race, they also have 1 or 2 of these same mats placed on the exit path -- every runner exiting will cross over at least one. This provides the family member or friend who is tracking you in the app yet one more location and time to help you know how much longer it will be before you and your runner meet up at a hopefully pre-set location.