I've recently managed to get 3D accelerated graphics working on my laptop with a Radeon HD 7520G. I'm using the default Xorg driver (i.e., not the proprietary ones which seem to create worse problems like breaking X).
running /usr/lib/nux/unity_support_test -p produces:
OpenGL vendor string: X.Org
OpenGL renderer string: Gallium 0.4 on AMD ARUBA
OpenGL version string: 2.1 Mesa 9.0
Not software rendered: yes
Not blacklisted: yes
GLX fbconfig: yes
GLX texture from pixmap: yes
GL npot or rect textures: yes
GL vertex program: yes
GL fragment program: yes
GL vertex buffer object: yes
GL framebuffer object: yes
GL version is 1.4+: yes
Unity 3D supported: yes
Which is all good (the "Not software rendered" used to say no, for instance). Video playback is great. Unfortunately games (and glxgears) produce really bad video tearing (or artifacts -- not sure the proper technical terms but whatever it is it looks very bad). I've found advice on editing xorg.conf to try different options to fix the problem. The problem is that there is no xorg.conf file (apparently it's no longer needed?). When I try to create one or copy one from somewhere else either I lose the accelerated graphics completely or X is no longer able to start.
I guess what I need is a working xorg.conf file for my situation which I can then play with to see if any options will help my situation.
Alternately, any other solutions to the tearing would be appreciated (that most likely do not include the proprietary drivers as they seem to break my system).