The bad first. My system really really didn't like it. Everything got messed up. Evolution ground to a halt - checking email would take ~ 1/2 hour to retrieve a single email, highlighting a message would take ~ 3 minutes and max the CPU. Epiphany / firefox just hogged the CPU to the point of unusablilty. Programs would randomly crash or fail to start. Basically, the worst system I've ever seen.
So, I struggled. I tried to fix the system, to make it usable. Alas, on Sunday I gave it up. I decided enough was enough and it was time to reinstall. Reinstalling is an arduous process for me. I'm an Emacs user. Everything has to be set up just-so, or it feels wrong. So, I am currently in the process of setting things up again.
However, even now this has turned into a good thing. I've been using the same base system since Dapper and it was beginning to age a little. The fonts had been broken for a while (they were a horrendous bodge that I'd forgotten about). It's odd to see real fonts again. The fancy desktop effects finally work and are sane enough to try using (they're not annoying me yet). Everything feels faster, more responsive. There's also loads of installed packages that were obsolete and many that were missing that should have been installed.
All in all, I'm liking my new system. Even if I have to spend hours and hours rebuilding jhbuild, setting up all my apps to be perfect and teaching the panel to know how I like my system.