It loads and connects, the window is fairly small but not entirely impractical. Unfortunately I can't move.
On the desktop, the cursor is changed and moving the mouse around highlights squares, clicking on one moves your character to that square. No such things happen here. I am stationary. Won't even highlight tiles. I can click on the various icons and menus and stuff, but that's useless if you can't interact with the world.
On a plus note, I did see some other users move through my view, and while they were fairly choppy it wasn't game breakingly so, seeming to move tile by tile in jumps instead of fluidly like on the desktop.
edit: and this is at stock 500Mhz.... oh, someone just killed a rat. There was sound. Neat. I hadn't realized the FF on Pandora ever made any sound. Facebook certainly doesn't. Also note that it takes a fair chunk of RAM. I'm 40MB into my swap file and FF with this one tab is the only thing running.