Yes - the game is very enjoyable without max setting.
Personally, I play on my Gaming PC at max settings, my bro's computer at medium setting and my laptop at min settings.
The game looks good, even at minimum settings. With medium settings, you will be happy.
Other things to be considered for good performance:
- RAM - you want at least 512 megs of RAM to avoid slowdown in populated/busy areas
- Monitor - DON'T get a cheap LCD with 25 MS response time. If you want a nice picture, make sure you either get a CRT (box) monitor or an LCD with a refresh rate of 75 Hz and a response time of 16 MS or better.
If you're concerned with budget, go with the x300 SE 128 meg. It's a decent card from what I've read, and great bang for your buck. On a good system, it might be able to run max settings, and will definitely perform very well with medium settings.
Good luck and happy hunting!