Then when I move the window, or switch to it with Exposé, it's resized back above the dock.
Well, the only thing that's blocked by the dock in Firefox is the middle of the status bar and a few pixels at the very bottom of websites (two lines of Copyright text hidden on MR, oh lawd), which is nothing. But when the dock pushes the window up, it takes up 55 pixels and the full width of my screen, and puts the status bar on top of it, which is only used for the left and right sides and is a waste of space.
Basically, with the dock above the window, it takes up 923x28 pixels, and with the dock pushing the window it's 1680x75 pixels. It also looks horrible and makes the dock's reflection look worse 'cause it's just a darkened part of your desktop and a small grey bar at the bottom, staying the same. Having the dock over windows does block stuff in some applications, but that's what resizing is for.
What I'd really like to see is a snapping effect with resizing.