Well, while I am sure you are very used to your UI, for me, I see 2 critical flaws.
#1, your main chat and your group HP windows are too far apart. Like yours, my set up has my main chat and group windows are side by side. I can't begin to tell you how important that is to me, since I type by looking at the keyboard, and I can't be looking around my screen to read, and look at group bars, and look at my keyboard. They just have to be closer for me. But on yours, the chat is over on the left side of your chat window, which would me bad for me.
#2, for me, not using view port doesn't work. I either have trouble reading the chat windows, or I have to darken the chat windows to read them, which blocks my view.
All in all, the same basic principles I am trying to get across.
