Summary: Got this card years ago; I remember how stoked I was to finally have a video card suitable for gaming. It was used when I got it, but even so, it's still humming along rather happily in one of my older AGP-motherboarded PCs. It had some overheating issues for awhile (would eventually shut itself off while playing more intensive games). An aftermarket heatsink/fan fixed that issue.
Summary: I benchmarked this GPU and GF6800GT. X800 Gives me ~9,400 Marks (Tested w/ 3DMarks03, P4 3.2, 1GB DDRRAM) and 6800GT Gone up to ~10,800 Marks. But technical specs are same. Except X800 does not support Vertex Shader 3. So I gives X800Pro 4 Stars.