Article author here. Anecdotally the battery life takes a bit of a hit, but I've been running it pretty hard to get everything installed. I haven't done any tests. I have a suspicion that Chrome limits its CPU usage, and the chroot does not. That said, the battery life isn't completely shot in the chroot.

I got my Chromebook on Monday, so I haven't updated it after initial boot. I'm not sure about the updating issues, but you can always go into non-Developer Mode and update from there. If that causes problems for the chroot, it's really easy to back up the chroot (it's just a directory) and reinstall it with Crouton: https://github.com/dnschneid/crouton#you-want-to-make-a-boot...

So in other words, I can't answer any of those questions yet, sorry!