Am I the only person who dislikes the new user interface? It does look nice and shiny and all, but having a separate window for every chat tends to get quite messy. I'd rather see a tabbed interface like in RTB 2.0-3.5's IRC.
Also, I'd also like to see some changes done to the add-on manager. The system works pretty well, but the design could be better. Small, gray text on a light-grey background isn't very easy to read, especially not on my dedi's CRT monitor.