Any problems with QuickTime, other than what I read in another post here about it being a pain trying to always label itself as the default player? (Which I’m assuming you can change?) Was trying to listen to something on a site for work, and it said I needed to download it to listen. I’m getting a lot pickier now about what I download! 
I have QuickTime installed and it does not mess the file associations (you can set while installing and after that into its settings).
I don’t have quicktime, but use quick alternative.
I too don’t like the way it wants to take over the world if you don’t reverse defaults when installing and after updates it tries it on again.
Take care on updates as the orchard will try and slip safari past you as well and possibly itunes or is it the other way round if you have itunes it will try an slip safari and quicktime past you. In any case read any update screens, don’t take anything at face value and whatch for what is selected for update/installation.