Everything...except for the most important feature of Unreal Editor
What does not
Grabbing and rotating, zooming, or any form of toying with the viewports.
What was not tested
Even though I was able to open an existing map from my copy of Unreal Tournament GOTY, which worked nicely and allowed me to adjust textures on the surfaces I was able to touch in the viewports, due to the lack of ability to move things in the viewports I couldn't work on a map from scratch to end.
Right now, if you were to try and run UnrealEd 2.0 with no modifications to Wine, it would fail loading the GUI. In order to get it to run, you have to hack the bitblt.c file in the wine source under the gdi32 dll folder. There are more details on that under the bug listed for this (it's linked to UnrealEd 3 so look under that and you'll be able to access it without searching :D). It's a pretty simplistic hack, and it could cause some issues on other programs, but I've tested xfire, RealOne, and some other programs and it didn't show any issues.
|openSUSE 13.1 x86_64
|Aug 26 2014
|openSUSE 11.4 x86_64
|Jul 03 2011
|Ubuntu 9.04 "Jaunty" amd64 (+ variants like Kubuntu)
|Oct 22 2009
|Ubuntu 8.10 "Intrepid" i386 (+ variants like Kubuntu)
|Aug 22 2009
|an anonymous user
|Ubuntu 8.04 "Hardy" i386 (+ variants like Kubuntu)
|Oct 04 2008