For those that may be looking for holiday shopping deals on new graphics cards, be forewarned that the Radeon HD 7000 series on the open-source code is still a mess. There has been kernel mode-setting support and other basic functionality, but 2D/3D is still rather non-existent. There is the "RadeonSI" Gallium3D driver still being worked on and it can handle some basic 3D demos, but it isn't yet in a good shape where it can meet user's expectations. The 2D support for the HD 7000 series on Linux is now being piped over the GLAMOR library to use 3D, which also means that support there can be less than desirable too until this new 3D driver is made fit.
Hopefully in the next few months we will see all of the bugs worked out and the RadeonSI Gallium3D driver made in a state comparable to that of the widely-used R600g driver, but we're not there yet. For the average Linux desktop user, you won't see good enough support until around April when Ubuntu 13.04 and other new distributions get rolled out, which will have been well after a year of the hardware's availability.
If you're shopping for a new AMD graphics card this holiday season, it's best off sticking to the Radeon HD 5000/6000 series graphics cards. There the support on the open-source driver is in fairly good shape although the performance doesn't match the Catalyst driver, but there is the Catalyst driver you can use too with the HD 4000 series support and prior having already been dropped from the binary blob. In another post will be additional shopping advice for Linux users looking towards new hardware this holiday season.
Some of the still-open Radeon HD 7000 Southern Islands tasks are outlined on this DRI Wiki page.