Just a heads up. My site had been slowing down considerably lately and even crashing at times due to high server loads. After trying to diagnose the problem with no luck I decided to disable the WP-PostRatings plugin I had installed and like a miracle all the problems my server had been having cleared up. The little bastard was just using so many resources the server couldn't handle it.
I'm not saying you should stay away from it completely, but in my case I was using it heavily and it just bogged down my server so much.