1) iOS maps suck (and it is related to data of maps, there are many places they are not accurate. Course your mileage may vary but problem is when you don't know an area, do you want to rely on a map that may or may not be reliable?). I'm just hoping Apple puts in a lot of effort into this (cause it won't just take a little) and they improve.
2) Some people are remarking about scuffs out of the box. I suspect it is a manufacturer defect vs. chips easily. I did watch one video where he tried to scratch the back and sides with a key and knife. If he stabbed at the back it did create little holes (his camera wasn't picking them up but he remarked it had "holes" so I suspect they are small and not so noticeable). It did chip easy on the corners (which is no surprise, anodizing tends to chip/wear on corners). I also wonder how quickly the anodization will wear out over time honestly (things I've had with anodization eventually the color wears thin). But that is a time will tell thing.
3) There are some people saying they are having wi-fi connection/slowness problems. This isn't getting as much airtime as the other two problems so I suspect it's not as common (because honestly, I would say this is definitely worse than 2 or 1 <- because at least with 1 you can download other map apps as a work around and 2 is purely cosmetic. I think 2 is the least of the problems here honestly but I listed the issues more in how many people seem to be complaining about it vs. how bad a problem they are).
Other than these three things I haven't seen much else that really stands out as might be more than an oddball problem.