In no particular order, just some things I've seen that would be nice to have addressed:

- The ability to add a note to people on your friends list. (So you know why they're there).

- The ability to make your own mapnotes (to keep track of things like which areas have which gathering nodes and mobs and such)

- The ability to right-click and Add to Blacklist from chat (it's at least an easy fix until the gold spammers get taken care of)

- A preview window for items and dye colors, etc.