I have Quicktime on Windows and it r00lz. It's not as good as Mac Quicktime, but that is because the Mac is from the future.
On a Mac Quicktime is totally integrated (there's that world again) into the system and I don't even notice its there. Its just whatever runs when I play video/audio. So, its pretty much like Media Player...9, was it? Whatever the last non-ultra-annoying version of WMP was in Windows. And like WMP in Windows it will use whatever codecs and compressors that are in the QT library folder (which on my Mac is pretty much everything).
Under Windows though it really stinks. Its this "other" app that is separate from everything, and if you are going to use something separate from everything you are better off with VLC. Its also popping up all the time and asking you to update even if you haven't touched the program since the last update.
This is not exactly surprising. Safari under Windows is kind of pointless too since its operating in a vacuum without all the other cool Mac stuff to back it up. Once again, if you are going to use something non-integrated you might as well use Firefox.