I've used low end nvidia cards on various linux boxes for years with no issues at all. Video plays. 2D works. 3D works. You would think an ATI card costing 4-6X would work better, right?

You'd be wrong. Googled around, and like everyone else, I'm shocked at how badly these cards are supported under Linux. Search for choppy video, tearing video, or whatever else you like. You'll find that it's been broken since 2006, if not earlier. Guess I need to spend another $40 and get myself a smoking hot nvidia card. Sheesh.