On the downside, I was a bit disappointed when I realize you can't fix all of your Registry issues in the trial version, and also when I saw that most Windows tools in PC Tools Registry Mechanic were actually built-in system tools.
While we can't say for certain that we noticed any dramatic performance increases having run the software, things did seem fractionally smoother and our system was certainly no worse off after its brush with this comprehensive and easy-to-use suite of Registry tools.