Nah, Minimum specs = Ati x800pro or better ATI video card
Really, this game is having issues with most all Nvidia cards from what I've been reading on the offical forums. There's a lot of pissed off 6600/6800 users out there..
Anyhow, here's what you can do to improve performance:
1. Download the 1.1 patch - it doesn't really improve performance, but fixes some major crashes.
2. This is the best performance improver, but you lose a lot of visual quality: Edit the game's \data\graphics.config file.
Scroll down to your video card, and take a look at the numbers to its right. 3 0 3 is the highest quality setting. The middle number has the biggest impact on performance, so set it to 3 1 3 to lower the quality one step.
The 3 1 3 setting will look a bit worse, but will make the game much faster on about any geforce 4, 5, or 6 series. This should also work well for the radeon x300, x600, x700, 9700 and 9800 if you're not getting good performance already.
3. Change your card's pixel shader to 2.0 instead of the default 3.0. (the game was optimized for ati cards that use ps 2.0). The only app that does this that I know of is nvhardpage which can be downloaded here:
http://www.guru3d.com/nvhardpage
Run the program, and go to DirectX / Shader Settings. Click override shader settings and set the pixel shader to 2.0. You may need to reboot before this works properly.
4. Some people have changed their PCI latency and have noticed some improvement (supposedly for AGP cards only). Download PCI latency tool from here:
http://downloads.guru3d.com/download.php?det=951
Open it up and you should see your card with a latency number next to it. My default latency was 240, and it was suggested I change it to 24.
Apply and save through the settings menu. Reboot to be sure it saves.
I didn't notice any difference by changing pci latency, but it won't hurt to try.
5. Wait for the next patch

Most everyone with a nvidia card is having disapointing framerates and Lionhead is getting a lot of heat for it. Hopefully they'll incorporate some nvidia improvements in the next patch.