Never let a shareware do a user's job... I don't know if "RegSeeker" is compatible with Vista, but I have been using it for a while on XP. It does a good job, and it's really free. Cleaning the registry is important, but regarding services and such, disabling them should be done manually.
vLite is a fantastic program for editing Vista before its installed. Basically you unload the image onto your harddrive in XP using this vLite program, and it allows you to edit how Vista is installed on your PC.
It allows you to completely autonomize the installation, by entering your CD key and other necessary information, into the program. You will most likely be able to streamline any future service packs (might not be added as there are no service packs for vista yet) but it was present in nLite, which is the hugely popular XP version. You can also add drivers, remove software, set priveledges and users, all sorts of things you can do with it.
Once you finish making your changes, you can then burn a new Image to a disk and use that as your Vista install disk. Works like a charm.
I'm using both of them. vLite is still green, but nLite it's awesome. Mix nLite with RyanVM's service pack (integrates all the hotfixes to date), and you'll have an excellent version of XP. Let's hope we can do the same with vLite in the future. The resources consumed by some of Vista's functions are too excessive. The Explorer using Aero eats an average of 57mb, and the Sidebar grabs another 50. That's 107mb. Memory is cheap, yes, but it's too much, and once again, you cannot choose what to install in Vista...
As per what Ethaniel said, he is right. But so far what I have noticed is when loading a game, the side bar and Aero shut off and then restart once you exit the game.
I have found though that tweaking or optimizing Vista is a little more difficult than in XP. ALthough the Auto defrag setup is nice. Being able to set it to defrag on which day at what time helps for those who don't forget.
I guess I'll try TweakVista then see how it works.