Works pretty well, software compatibility isn't the biggest gripe about XP right now.
Most of it relates to hardware. With beta 2(build 2562) you'd get random reboots now and then.
Phillips AE sound cards suck in XP. My Nvidia card would freeze the system when exiting an OpenGL game (counter-strike) every once in a while. However, everyday new drivers are released that support XP.
Personally I don't mess with beta operating systems unless I can dual boot or I have a second machine to do it with. When I ran XP Beta 2 I noticed that it ran really nice at first then slowly the stability degraded a lot.