I use it, and yes the things it changes never really mess anything up. But i dont really notice a difference after i use it. The things it lists are safe so dont worry about that.
I use it, and the only problem I have ever had with it is it uninstalls MSN messenger whenever I fix the problems it comes up with. It's doing it now actually, quite annoying. Other than that it's great.
I dont evan use anything like that, I cant stand the idea of a program messing with my registry. If I want to tidy up my registry, I just repair XP - and I make a backup before I install and uninstall anything.