Been using X64 for about the last 18 months and it will truly be a sad day if and when it stops getting supported, in that 18 months I can honestly say I have not had one single driver finding issue. I dual booted with vista64 and nothing worked on that OS (I hear its improved a lot though, but i cant bring myself to go back to it unless I really really have to) so ditched it after not using it for 9 months solid and needed the drive space for the other boot.
similarly i've not had any software issues either, games, Autocad, 3DSmax, Kav, Sketchup + Vray all run like a dream
People who say XP64 is poor/unstable/has no driver support have simply never used it.
LOAM