On the factory images page, there are downloads for the Wi-Fi Nexus 9, Wi-Fi Nexus 7 (2013), and the Nexus 10, and we're expecting updates for the rest of the Nexus devices soon.Android 5.0.1 released; fixes inadvertent factory reset bug
Google hasn't said anything official about the update, but Peter Kiddier, an intrepid commenter over at Android Police, has picked out the new commits from the source code. The major showstopper looks to be this bug, which, in some instances, could cause stray input on the lock screen to erase everything on the device.
The bug sounds rare, since you'll have to set up certain security policies to risk triggering it. Android can be configured to wipe the device if the user fails the lock screen security challenge too many times. When combined with some lock screens, the security lockout could be accidentally triggered by stray input—for instance, from the phone rattling around in a bag or pocket. The most susceptible is the pattern unlock screen, which has the user connect a grid of dots to unlock the device. This is normally done in a single sweeping motion, but Android 5.0 will count a single tap on the pattern screen as a "failed attempt."