I can only infer that 3d acceleration works by way of noticing that I don't have any problems.
I can't speak on the issue of using the drivers with the newer ATI cards. There have been so many requests for help in these forums, each mentioning one specific ATI card, that I would suggest searching for these posts via the LQ advanced search page. Maybe one or more of the people who have responded to these requests have included information about their experience with using these drivers on newer cards.
As for me, I have become an enthusiastic advocate of Nvidia products. I am particularly fond of their motherboard chips and their graphic drivers for Linux. I get suspicious if I mix Nvidia motherboard chips with an ATI graphic card and then have any problem so I purchase the Nvidia graphic card mostly to match the Nvidia motherboard chips.