I agree on the lack of chat space, although I like to keep all my chats in one tabbed window instead of several like others prefer. I'm not an officer though, so I may not have to pay attention to many different channels that others need.

The chat window takes up a good 1/4 of my screen at 1920x1200

I usually have my main window show guild chat, party, raid, whispers, and general (nobody talks in general). In a second tab, I have trade. In a third, I have guild only (for catching up). In a fourth tab I have party,raid, whisper and events only for when I want to focus on raiding.
The fifth tab is whisper only.

One big big suggestion to this week's UI, get rid of all those buff icons and get OPIE!
http://www.wow.com/2008/06/29/addon-spotlight-opie/
You can probably eliminate most of your buttons and make room for a lot more stuff.
The only things that should be visible should be stuff you actually constantly need, and I doubt anybody is actively buffing during a fight unless right after a tank death and battle rez. Even auras can be put on a ring and hidden most of the time.