For what it's worth, I have the same problem. I've found that the quicktime export yields better resolution for the file size but a flatter, washed out look.
It sounds like the issue may be related to the Quicktime player. Maybe try using a different player? I rather like The KMPlayer myself.
+1 for KMPlayer.
I have battled this "gamma/bright" issue since going to a totally tapeless workflow.
My workflow by virtue of my post house facilities includes passing files (QT, seq. tiff/tga, avi) from (my PC) thru' FCP and Kona Cards to get mastered to Broadcast media. Unavoidably includes a Mac and QT part in the process.
I have tested the workflow by exporting same timeline to files and DV tape and compared the outputs at the same facilities.
This year, I am determined to find or create my own "broadcast filter /settings" to resolve this issue.
This is a bigger problem than the player. Good luck and keep us posted Craig!
I did not read the below again, but I think this is the piece in which he explains why Jimmy's attempt in the OP (the "blend" in movie properties) does not work (or at least no longer works).
Quicktime has a feature, mostly hidden from users, which is designed to adjust the display gamma of quicktime movies on different machines to compensate for display difference. Deep within the file, there is sometimes a little tag called 'gama' lurking which tells the Quicktime player what gamma correction the file was encoded with. While this is well-intentioned, motivated by the difference in display gamma between PCs and Macs, the Quicktime player offers no way to view this tag and change it.
To work around this issue, Frantic Films Software "created a small tool that strips the 'gama' tag out of offending quicktimes. It's a very simple tool which operates on all the file names and folders given to it."
This QuicktimeGammaStripper utility (for Windows) disappeared in the last few months, but it popped up here http://rapidshare.com/files/124507779/QuicktimeGammaStripper.zip
AFAIK the way QT displays your movie is NOT an accurate respresentation of the movie itself, but an attempt to adjust to the type of system you have. Stripping out the gamma setting 'fixes' this. If the QT movie is uploaded to, say YouTube, this gamma is stripped out as a matter of course.