Thought it was just me but yes - iPhone 5 getting noticeably warmer. Battery life was also a bit lower (I usually get to the end of the day with about 70% left, today I had 47% when I plugged it in. iOS7 had been installed about 2 hours.
I also noticed it was very laggy and getting very warm just after install
I also did a hard reset and a soft reset and now it runs as normal and no more lag.
I waiting to do this until all my apps had updated in the background.
I've noticed some quirky behaviour like location services sticking on in camera app and turning on when i unlock my phone. Wifi also cycles a lot more, especially on fringe areas i.e. my office. I get low signal to my phone but ios6 held the signal fine, ios7 cycles rapidly.
Look at your usage. I had 2 hours and 35 minutes since charge, and 2 hours 32 minutes usage. Something was keeping the CPU awake and eating battery while generating heat. Restarted and charging again to try and figure out which app it was.
Downloading all your apps en masse will do that. Had the same problem with iOS 6 GM. It'll sort itself out once everything is downloaded.
Spoke too soon. Finished downloading all the apps, hard rebooted, still having battery issues. Chewed through 25% of my 4S battery during a 30 minute haircut. Yikes. Trying turning off motion and a couple other services to see what might be causing it.
Try disabling some system location services. I found that weather often uses my location a lot (for some reason) and that warms my phone more so than when I stream content on netflix, but alas I want weather to keep determining my location.
At idle though, my phone is cool to the touch.
Edit: you guys also might wanna check 'background app refresh" although mine is turned on and I don't get that constant warming, so that probably isn't it.
I solved my battery / overheating issue. I had noticed that I had text messages coming in without names. When I checked, I had a bunch of missing contacts. Turns out my secondary iCloud account with my personal contacts in it was set up, but wasn't syncing, so it was stuck in a loop. Deleted it, readded it, and now my overheating and battery issues are gone.
My iPhone 5 has been fine but this afternoon an iPhone 4S I use for development which I installed iOS7 on yesterday got very hot, certainly more than just warm. It seemed to be at the back about level with the volume buttons. I did a hard reset rather than investigate what was causing it though. I'll be filing a bug report with Apple.
Phone always seems to be warm and every time I try to use the turn by turn navigation while playing music the phone actually gives me a message on the screen about overheating and shuts down one or the other.