I'm using Firefox, and I can resize this window quite small. The only pages that need scrolling are the Post Window and ones with large images. IE seems to be pretty similar (I could get Firefox a little smaller before it needed to scroll)
By default I use 1152*864, so I have no problems
BSM, if you're having difficulties, try turning down the font size in your View Menu -> Text Size. I use Medium myself.
LD