I have only really tried games so far
BF2, no problems, actually runs sweeter imo.
Fraps, no problems.
CSS, No problems.
DoW/WA, No problems.
Real Player, QT and so on no issues.
FEAR/Combat, runs better than on Beta 2 also imo.
CCleaner works but its more effective if you add a custom file to clean to get it to clean the IE files accurately.
Xfire and teamspeak work.
Punkbuster might have issues on some servers (BF2 and FEAR have shown this) unless you disable UAC/UAP.
I'm going to risk using this as my main OS for a bit, im that impressed.