I purchased one of these "pre-overclocked" cards from Extreme-PC. And while I have no experience with stock cards, this card does offer excellent performance in DX9 titles with the newest driver release. However, I am still disappointed in the overall price/performance levels I have been getting...
I feel the same way. I have an HD2900XT 1GB and I am seriously considering selling it for a loss and picking up an 8800GTX until something better comes out.
The clocks you see in Windows are the 2D clocks. All new ATI cards downclock to lower speeds while not in 3D applications. As soon as you launch a full-screen 3D program (ie: games), the clocks will up themselves to the requested clocks (usually the advertised clocks).
So ... what you are...