I haven't specifically had compatibility problems with QuickTime, but I avoid installing it because when I have it insists on installing shortcuts on the desktop and in my QuickLaunch bar and it insists on running a component at startup (which sits in the tray), apparently to check for updates. And if you try disabling the startup item with msconfig, it comes back the next time you use QuickTime. At least that's what I recall.
Exactly. It tries to take control of all the media without offering an opportunity to do otherwise.