It is improving. But very slowly. When compared to Windows, the changes there can be drastic between Catalyst releases. We've had cases there where in one month we had a "all bugs fixed, 100% speedup, a dozen new features" Windows release.
The Linux versions look quite pathetic compared to that.
I guess I should add that overall, it's working better than I expected (the ati part, I've always used amd). So, I guess I'm somewhat pleasantly surprised that the promises made by amd to at least give a good effort for linux, both on the binary blob and open source documentation are bearing some fruits. Sour maybe, but with time, a sour orange can become sweet