It is a fact that the
Windows-implementation of
QuickTime is rather bad because
Microsoft have held back
APIs and even took lengths to make
QT perform worse than
Mediaplayer (there are specific functions in
Windows that prevent
QT from working in an optimal manner - refer to the
Microsoft Antitrust Testimonials by
Avie Tevanian).
Aside from that, some of the QT codecs are excellent (Sorenson, etc). The abysmal volume control mentioned has also been fixed in version 5 and is now much more convenient (wheel vs. bar).
As a side-node, I have had bad experience working with QuickTime on PCs because of the aforementioned Microsoft-harrasment (sorry for sounding biased, I can't help it. Up/Downvote as you please), while having quite good experiences working with it on Macintosh.