well i havent had windows installed on this machine in over a year, but i can say that my machine was never FAST with windows.
btw, my computer is a Pentium4m 2.4ghz with 512mb ram. Right now i am running feisty fawn fresh install with beryl setup with transparencies and wobbly windows and all and i am not noticing ANY lag. things are very snappy, and very cool looking for the minimal amount of tweaking that ive done