I wanted to post an update on our GPU3 beta test. It is going well, so we have put the GPU3 client on our high performance client download page. This new client is required for all Fermi hardware, but also allows pre-Fermi NVIDIA GPUs to access the new GPU3 cores. These cores are labeled core15 (which has already been extensively tested and is in production right now) as well as a new core16 which will be appearing in testing in the coming weeks.
We are also working to finish our OpenCL port for ATI GPUs to support GPU3 on ATI, but there are still performance issues for OpenCL on both NVIDIA and ATI which are holding back this release. You can see more information about the key software behind the GPU3 cores at the OpenMM project website. If you're curious, there is openCL code there for NVIDIA and ATI and we invite the open source OpenCL community to check out this code and see how they can help if interested (note the code is released under an LGPL license).