i've been using these for a few days and have yet to find any issues with my games.
if any other gamer is using these 10.3a drivers, i would recomend the "first Catalyst external profile update" over at rage3D
i've been using this today and playing bfbc2, and even though the update readme states the bfbc2 update is for crossfire, myself and others at the EA forums
have noticed improvements even on single cards.
i've got the one 4890, and i haven't done any proper benchmarking, but for me framerates seem to be slightly improved.
more noticeable is better looking aa - it used to look truly awful, now it only looks bad!
the new profiles are not a whole new set of drivers, but a new bunch of cat ai enhancements for a handful of new games (i think) - anyway, it's only a 488k download.
some users have reported problems - if so, they are easy to uninstall.
...or you may prefer to wait until official release...