With the multi-sample anti-aliasing (MSAA) for Cayman plus flipping on the OpenGL transform feedback support, this latest hardware to be supported by the R600g driver now exposes GL3 compliance. These were the remaining bits to properly advertising OpenGL 3.0 on R600g for Cayman.
This also represents a bigger milestone since now all GL3-capable hardware supported by R600g from the Radeon HD 2000 series through Radeon HD 6000 series now properly advertises OpenGL 3.0 support. Too bad though the Radeon HD 7000 series support isn't in good shape.
This new patch series can be found here and should make it to be part of the next Mesa 9.0 release.