I can honestly say I havent once had a reboot and ive had mine for about 4 weeks now.
Then again i got one with no light bleed at all either...
Random Reboots / Major Instability
Known affected devices: Nexus 10, Nexus 7, Galaxy Nexus, Nexus 4.
Documented? Android bugs       , XDA   , Google+.
File this one under "critical," as well. I myself have experienced this bug - my Nexus 7 rebooted no less than 4 times this weekend, several when it was just sitting idle with the display off. That's... bad. I've since done a factory reset, and in the last hour, so far so good. You'd think a problem this serious would be limited to a pretty specific subset of hardware, but no - everything but the Nexus 4 is affected (which seems to be the case for every one some of these bugs, oddly) all Nexus devices appear to be affected (thanks for the input about the Nexus 4, guys). The reboots occur when opening webpages in Chrome, using Play Magazines, and a variety of other circumstances (like doing nothing at all).
Nexus 10 users are apparently the most-irked when it comes to the reboot issues, with them often occurring multiple times a day. The behavior described sounds a lot like a kernel panic - total system lockup while in the middle of a task, followed by a soft reset. Video playback seems to be one suspect for these lock-ups across all affected devices, with the YouTube app having been cited several times in various postings.
The reboots aren't the only problem, though. On Galaxy Nexuses and Nexus 7's (eg, devices upgraded from Android 4.1.2), performance has taken a complete nosedive. Opening apps, Google Now, or navigating through the UI has become much slower in some cases. I noticed this when I upgraded, too - all that butteryness suddenly got a little less smooth. However, after a factory reset, I noticed marked speed improvements in the UI generally. Personally, this is where I immediately go if I'm having performance problems (and haven't recently installed a new app). There's no use in complaining about it if you haven't tried it already, because that's just what Google's going to tell everyone to do eventually.
However, many posters in various Android bug threads are reporting that factory resets don't alleviate any of these issues - which is highly concerning.
The stability problems don't end there. Galaxy Nexus owners are saying that their phones' displays are randomly turning on without any interaction. The system clock's time is off by anywhere from 3 to 10 minutes when set to "Network Time" for some. Apps are force closing for no apparent reason. For an incremental update, Android 4.2 sure seems to be causing all the problems associated with a much more significant OS release.