When a new program asks you if you'd like to create a system restore point before you finish installing it, there's only one reasonable conclusion: something bad could happen to the computer, the programmers know this, and so they're offering you a bit of Teflon for protection.
In TweakVI, the Windows Vista settings utility, it's a mighty fine idea to take the advice and create the restore point. It's not that the program hosed my computer when I installed it, but it's definitely a buggy program and the current version, at least, should be avoided for now.
The installation itself raised the most red flags out of anything I did with it. Twice it froze on me during two different installation cycles, only to unfreeze nearly five minutes later. Since I regularly install and uninstall programs, and haven't encountered that quirk with any other applications, I'm fairly confident that it's a TweakVI bug.
There's also a nag screen, and the well-designed main window opens a new window for whichever options you decide to explore. Both windows look good and are easy to use, but given the light volume of content in the main window this secondary one just seems gratuitous and time-consuming. Other bugs include: not saving some settings after a reboot and failing to revert other settings to default after uninstalling. If you do test TweakVI, test with caution.
All of which is a shame, because the utility offers some great desktop enhancements. There's lightweight fare such as removing the arrows on shortcut icons and helpful tweaks like taskbar reboot/standby/shutdown buttons colored to resemble traffic lights. There is also plenty to appeal to power users, with tweaks for serious power management and system behavior changes that can for example, adjust your CPU cache.
There's also a paid version, which kills the nag screen and offers users more features such as RAM optimization. TweakVI has the potential to be a fantastic Vista tool, but only those dying of curiosity--or those wanting to flirt with headaches--should give this program a try.