unset LIBGL_ALWAYS_SOFTWARE; /usr/lib/nux/unity_support_test -p

yields:
unset LIBGL_ALWAYS_SOFTWARE; /usr/lib/nux/unity_support_test -p
OpenGL vendor string:   X.Org R300 Project
OpenGL renderer string: Gallium 0.4 on ATI RV350
OpenGL version string:  2.1 Mesa 9.2.1

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

***

I assume (don't know how to test and gdm is not installed) lightdm is my
display manager, I reinstalled lightdm but no change. Logs look ok, I am going
to restart without software rendering (so X fails and I get kicked back to
login screen) and check those logs.