Six months or so ago, I went from a two-card dual-display setup to my Leadtek WinFast GeForce2 MX DH Pro. Note, this is one of the few non-mAtrox cards I'd seen that have two VGA connectors. All other versions had one VGA + one S-Video, one VGA + one DVI, or some other combination. So, be careful and take note of the card's output options.
I'm not big into gaming, but I went with my nVidia-based card in case I ever wanted to do anything requiring some 3D horsepower. TwinView (pre-27.xx drivers) was at least equivalent to having two cards in the same system, when it came to Win98/ME. The drivers allowed Windows to see each display individually and acted as if it is truly two separate cards. Win2K saw only one display, albeit with resolutions like 2048x768 or 1600x600 (twice the horizontal, with the monitors side-by-side). So, Win2K naturally maximazed across both displays and the taskbar covered both. nVidia tried to hack their drivers to make Win2K feel like it has two displays, but it was never there.
To date, I've only tried the 27.xx drivers on WinXP and its behavior is akin to that of Win98/ME. It does ad quite a few features that were not present in TwinView (multiple desktops, make "xyz" render faster, etc.). A definite improvement. I have not tried the new drivers yet on Win2K, as it is my primary and preferred-to-remain-stable environment.
-SUO