Fullscreen for me (1920 x 1080) with the game play area forced to 1024 x 800 by Razor. Gives me plenty of room for paperdoll / icons / containers while still being able to see the actual game. Then my 2nd monitor runs addons like UO Automap.
I just started the gump. Right now it is 900x500. In the end when I'm done coding it it'll be dynamic and size itself depending on what is being displayed.