Tabbed/customized chat system.
So it would be great if the general chat, system/quest messages, and whispers/tells could be be separated into different tabs, otherwise it's really hard to read what is going on.
World chat, Local Chat (with chat being shown above head also) and whisper chat.
Xio Rheims commented
Also it would be nice if chat was colored according to what kind of chat it was, for an 'all' tab, to cater to those who like having everything in one place. System/quest messages could be yellow, whispers could be purple, local chat could be white, etc.