I've been using OpenOffice since 1.0.something, and while it can be a bit slow to start up, I've had no problems with document compatibility except for the odd bizarre winmail.dat issue.
I think it's a shame that OO 2.0 has those gradient effects in the toolbars, just a pointless bell/whistle IMO. There's a ticket you can vote on to get an option to switch it off:
http://www.openoffice.org/issues/show_bug.cgi?id=40800
