The quality of the Radeon's drivers is debatable and the more I read, the more I'm convinced that they still have issues. For some people the card seems to work perfectly while for others it's a nightmare.
AFAIK, ATi does not produce their drivers in house, but rely on an outside company for them (I could be totally off on this though).
If that's true that would certainly explain the problems. Technically speaking ATi's hardware is sound; it's the drivers that let them down.