I've tried TC3-Test, and was able to play just fine. But yeah, there is some lag and choppy animation.
Speaking of DX10, I wonder what this game would look like with THAT! We may have some interesting water effects, clouds floating overhead from city view, and who knows what else.
Naturally, we would need to have an option for DX9 and 10, since not everyone (including me) really cares to upgrade to Vista.