This is probably the closest you get to an official Powertoy/TweakUI for Vista Tweak UI For Windows Vista : Ultimate Windows Tweaker From WinVistaClub - has that titel because some MVPs are involved I guess. How to get on Ars Technica, Life Hacker etc. Safe enough, there is a "Restore Defaults" on each window.
Much better to dig in to tips and tricks on Window sites like this, see Tutorials and use search. You dont need a tweaker. They rarely do anything but simple changes in registry, most even available through Windows GUI or at least command line already. Tweakers can be risky shortcuts for the lazy. At least this one dont come from a site with ads promising more speed and stability.
Retail? if you pay for a tweaker you are an idiot. Stuff like X-Setup could be worth it though http://www.x-setup.net/ for the very interested wanting to script tweaks etc. The normal popular tweaker must be free - if not avoided