After a flawless install, I restarted. Then nothing. The machine hung after running a few boot scripts. After a couple reboots, I got it into a terminal and found out that the new install messed up my X configuration. Simple but annoying. After a few tweaks, up and running. It's very nice.
I got home and upgraded. No problem here. No annoying X misconfiguration or hanging boot. But I'd give it a couple months if you're uncomfortable with making changes to xorg.conf.