This will only relate to those searching for ATI driver issues in Slackware: When installing the latest fglrx on a 64-bit multilib setup, DO NOT have it build a Slackware specific package. It will build a slackpkg for vanilla 64-bit instead of a multilib package, and things like TF2 will not load. When installing it, just select the first option that lists the xorg version. This won't create a package that pkgtool can see, but it will install all of the correct files.
At any rate that is just for those with HD5000 series and up. HD4000 series and below will have to use the legacy drivers.