I just read an article from ParanoidMike (Installshield – great for developers, sucks ass for victims (aka everyone else) where he does an excellent job of debugging an uninstall issue. He also rips InstallShield during the process.
Some of his conclusions are wrong, but that's not the point. It doesn't matter that it isn't InstallShield's job to support him ( Intel, where he happens to work, wrote the package ) . It only matters that when you are a company like InstallShield, it's always your fault. So while InstallShield 12 was a step in the right direction, it'll take years to be free of the legacy.