bobw: I think he's talking about previewing QuickTime movies IN the Finder... on your machine, if one part of the Finder freezes (like trying to connect to a server or something) can you still open another finder window, or browse files in the finder in some other location?
On my machine, sadly, no. If one aspect of the Finder hangs, the whole Finder hangs. It happens a LOT less under Panther than it did under Jaguar, though, so we definitely ARE getting better.