Lots of [excellent] talk about the Quadcore, but hardly anyone has really mentioned the 2900XT.
Before you buy it, and I hope you haven't bought it yet, I want to make something aware to you: The 2900XT does not compete with the 8800GTX. It's only designed to compete with the 8800GTS, and even then, it trades blows. If the games are ports over from the XBox360, then you will likely find the performance on the 2900XT to be spectacular, as fundamental core differences between the Xenos chip found on the XBox360 and the R600 chip found on the 2900XT aren't too entirely different. The shader core, however, is a completely different story, as the 320 stream processors on the R600 are extremely complex, capable, and powerful.
But therein lies the problem. The R600 (2900XT) is a fantastic chip, but ATI may have overestimated their capabilities in the ability to drive it along. Certain functions have changed between the R600 and the R500 series. When Anti-Aliasing (AA) and Anisotropic-Filtering (AF) are not enabled on the R600, it is quite a speed demon. Once you start cranking those visual goodies up though, the performance begins to plummet. Since many of the unique filtering methods (Wide/Narrow Tent) are handled on the Stream processors, the performance may or may not be improved with future driver revisions depending on the driver team's ability to manage the thread dispatcher (the thingy that controls what exactly those stream processors are doing: Pixel, Vertex, Geometry, or filtering equations).
The bottom line is this: The 2900XT is sometimes slower, sometimes faster than the 8800GTS. It costs more than the 8800GTS. It exhausts more heat and consumes more power than the 8800GT
X. It's not quite the debacle that the Nvidia FX series was, but in all honesty, as much as I love ATI cards, it's not quite the performance I was expecting this round.
Even still, it has a few things going for it:
-Console ports will probably run more smoothly using one.
-You can fold with it, and current performance is ~2.2x faster than current R580 speeds, though this ~2.2x performance level is NOT actually limited by the card itself. Supposed to be improved even more with time. Hey, some people like to fold!
-Driver improvement shows promise in boosting its performance. Still, this is not guaranteed.
So in conclusion, buy 3dfx!