1) The HP/Mana/Stamina/etc. window is just too big, and sucks up to much of the on-screen space. My suggestion is to get rid of the target HP bar, and simply show a small health bar under the name of characters. The range needed for the bar to appear should be rather close. (you have to be close enough to \"sense\" the status)
2) The FPS, time, and other little bits of info should be moved somewhere else. Sure, you can move the window so they\'re off-screen, but this is just a hack.
3) The chat window can easily be flooded with battle data, and actual chat messages often get lost in the clutter. I turn off most of the combat feedback, but even the damage reports are enough to clog things up. Using the tabs to avoid this gets annoying, because you can only see one of the chat types at once. (ie. say, tell, guild, group) Simple solution: Show damage done as a number that briefly hovers over the hit area of the target. (lots of RPG\'s do this) Again, you should have to be within attack range to see this. (yours or another player\'s)
4) Item/magic toolbelt. It would be nice to have a \"toolbelt\" that we could drop items/spells into that would sit under the stances icons. It would act like the shortcut window does now, but more compact and nicer looking. (Also prevent you from having to root through your inventory screen to eat some food or use a potion.)
5) Get rid of the \"started attacking\" messages. I see no point to these, frankly. If my stance on-screen changes, I\'m attacking. I don\'t really need a written record of it.
6) Allow the main toolbar to fade. I think this should have the same transparency options as everything else. You can hide it right now with a click, but an automatic fade away would be nice.
Most of these are fairly simple additions. Anyone have any other ideas?