I see posts from folks with fast GFX and fast CPUs who still complain about low frame rates in places that do not have heavy AI or the other known FR killers. I suspect their systems need housekeeping rather than upgrades.
As for those who claim that SSE is unplayable at 20 FPS, perhaps FRAPS doesn’t accurately report frame rate. One quick check on whether you are getting to low a frame rate is to, with camera 1 zoomed out on a busy scene, rotate the scene quickly with the mouse and stop quickly. If the scene coasts to a stop over several frames, you have a low FR.
The FR varies considerably depending upon the view. The difference can be 10 FPS between camera 1 zoomed out and camera 2 zoomed in on the overhead. (This is how you can get fastest mission time in 2008, where true speed varies with frame rate. I suspect that may be the case in SSE as well, but I’m waiting for an ME to test it.)