AMD's HD 2600 XT is a solid card that feels quite mature and works rock stable. Performance is a bit less than what I expected, especially to the X1xxx products the speed difference is quite small. On the other hand you get several new features like DirectX 10 support and the wonderful UVD high-definition video decode acceleration. Unlike NVIDIA's GeForce 8 Series, AMD gives you the whole multimedia package which consists of HDMI + Audio + HDCP.
While gaming performance of the HD 2600 XT is generally a bit slower than the GeForce 8600 GTS, the price is lower as well. In this market segment price is often more important than a few percent more or less performance.
The cooling solution of the 2600 XT works well, temperature controlled fan speeds keep the fan noise at a minimum. If you have a CrossFire capable motherboard you may run two HD 2600 XT cards in CrossFire, which should give you a healthy performance boost for a low price.