A handful of machines were failing uninstall-type Managed Installs (using Adobe's Uninstall, MSI uninstall commands, etc) and when trying to manually uninstall via Add/Remove Programs (which would give the annoying "missing source files" error). I've used these tools several times now and found them to be very useful (particulaly since the error typically points to a Temp subfolder which got purged months/years ago).
Definitely beats purging the software by hand from the registry and manually deleting program folders/files (which is what I've done for many years). The only thing improvement I would make would be to add an option to uninstall multiple applications in one shot, but other than that I can't complain.
These also have "Install Repair" functionality, but I can't speak for it since I haven't needed to use it yet. Just FYI, it's there as well.
XP & Vista
* requires an active Internet connection, works with proxy via IE settings
* portable version of FixIt app available for download