I edit my films when I make short films. You really don't need a top notch system to video edit, it only helps during rendering, and some playback of transitions or video effects. If you are just doing straight editing, not transitions or effects, you really don't need that great of a system for it to work. I just have my new system because I cant afford to buy a new system every time new tech comes out, so I get a better one to last me awhile longer before updating again. Plus it's nice to have a faster system anyway for those random effects I edit into my videos.
My software is Sony Vegas Movie Studio Platinum 7.