For a visual comparison I used a 4:3 ratio LCD to make things easy. I haven't loaded it on my laptop yet so I can't post any framerates atm, but it does give you an idea of what to expect visually. I forgot to lower the settings on the higher resolution images but it's not a major difference except for the glowing weapon.
640x480 Windowed - Low settings
640x480 Fullscreen - Low settings
1280x1024 - High settings
Even at 640x480 it's decent enough to be playable as long as you can get ok framerates without too much slowdown. The more I thought about it, the more I thought I recalled that the game may have been decently playable on my test laptop. Keep in mind though that I didn't get that far into the game at all, so other areas may be a lot worse framerate-wise. I'll post some framerates tomorrow using my laptop with the following specs:
1.6GHz Turion Processor
512MB DDR (I'll have to look at the speed, I don't remember off hand.)
Xpress 200M chipset
Since the expansion is coming out soon, we will probably be getting more tech questions about how it performs with x, y and z system setups.