Desktop : 1920x1200 on a 28" monitor
Laptop : 1920x1200 on a 17" screen
I use a lot of hotbars (15+ on all characters) and still have plenty of room.
But.... please make the UI resizeable. Especially the mouse cursor. Lost count how many times I've lost it in a fight with lots of spells effects going on.
Its been in the suggestions forum for over 2 years now and has got to be easy to implement :