Thus far I’ve run into two things that I’m used to that have changed: The upstart system init, and a problem with linux-686. Both of these issues are mine really, and one I’ve managed to circumvent — or adapt to.
I’m used to the old Dapper init, which spawned tty consoles from /etc/inittab. That’s where I was accustomed to putting the autologin executable, to avoid logging in and thereby speed up my start sequences. Call me crazy but life is nicer without gdm, kdm or any of the other *dm’s.
Post-Knot 2 Edgy uses upstart, and that login executable is prompted from an individual file inside /etc/event.d/. Easy enough.
The other is kind of strange. Upgrading to the linux-686 kills X for me, with both nvidia-glx and nvidia-glx-legacy complaining about no available devices. I’m still working with that one. Chances are it will be fixed by the time Edgy comes out in full, so it’s not really bothering me. And if it isn’t, I’ll chalk it up to a hardware peculiarity.