Every additional software on your operating system is an additional load which if not used is taking your computer down a little bit, so the best way to maintain a healthy operating system is to get rid of any unneeded software not used in your day to day tasks.
Basic Requirements
Open Source / Free / Trial
Simplicity
Advanced Features
Highly Maintained
Nice UI
Speed
Advanced Features ?
Uninstallers may come packed with several advanced features like
Removing Traces from Registry
Removing Traces from File System
Removing Empty Uninstall Entries
Registry Backup
OS Restore Point
Bulk Uninstall
Silent Uninstall
Which one is the Best Uninstaller ?
The best uninstaller is Bulk Crap Uninstaller, it just won in all categories, wiping out all competition.
It (one of the only which can do this one) removes software by bulk!
Removes traces of the installed software from any place
Is open source
Runs some of the uninstallers silently
The only downside to this one is that the UI is a little crappy and outdated, and the wizards are a little bulky, but once you get used to it, you won’t look anywhere else!