Hi, It's the linux kernel that contains the drivers. That is why you'll find the same problems with Ubuntu, Mint, Mandriva, all distros that use the same kernel. From reading the forums, there is a lot of work going on upstream (kernel developers) to fix these issues.
On a happier note, ATI, realising their faux-pas, have released the source code for their legacy drivers to the open-source community. This means open-source drivers will greatly be improved in the near future.
Ubuntu has many more developers, corporate support, etc. and they don't have a fix yet either!