While we dont have any detailed information or benchmark figures, we are hearing from sources in the Far East that Tessellation performance on the new AMD 6000 series cards is said to be significantly improved over current 5000 series offerings. This will be a great source of joy for the red followers.
Tessellation is a current strength of nVidia Fermi hardware and we can see this with performance figures in benchmarks such as Unigine's Heaven Benchmark, and the Stone Giant Benchmark – Nvidia's GTX460 mid range card is keeping up with the AMD HD5870 high end product for instance. Sadly, right now very few games are making use of Tessellation, apart from a handful, such as Metro 2033 but it is going to be a key factor in future titles coming out in 2011.
If you need to get educated on Tessellation, then hear it from nVidia directly, over here