Premiere Pro CS5 uses CUDA for rendering of some effects, whether that rendering is for preview or for final output. The same goes for scaling, deinterlacing, and blending modes (and maybe something else I'm forgetting, but I think that's it).
There are some circumstances in which processing falls back to the CPU, such as when the frame size is too large for the video RAM on a specific graphics card.
Adobe Media Encoder itself doesn't use CUDA processing, but Premiere Pro renders frames that it then hands off to Adobe Media Encoder for encoding. So, the first phase of this process---the Premiere Pro phase---can still be accelerated by CUDA processing. The encoding itself isn't CUDA-accelerated, though.
The encoding itself isn't CUDA-accelerated, though.
Thanks, Todd... I thought that was the case, but I've been a little confused about it myself, based on my understanding from posts on this board and then reading other materials, such as the Tom's Hardware reveiw mentioned by the OP. Glad to have it cleared up once and for all!