I really really really don't like Quicktime X.
Here's a rather unusual tip to view small movies at their correct size since QTX resizes and scales up smaller movies.
"To quickly view a movie without this restriction, I drag it into a new mail message. The player used in Mail has the old-style controller at the bottom, and plays the movies at the correct size."
It may be further evidence that QTX is just window dressing to the old standard QT core technology that's been around for a while now.