Sure, the UI is usable as is, but there's tons of room for improvement. I would prefer that they just start by ironing out some of the maddening bugs... such as the focus target setup.
Focus target works great for healers once you get it set up, however, you end up resetting it after virtually every cut scene (and when do you get into some of your toughest fights?). I typically have my companion set up as the focus, and there are times when I have to dismiss and resummon the companion befor I can set up the focus target again. Further, if you have the focus key held down at the moment your enemy is casting, you do not see his cast bar to interrupt.
Anyway... it's a young game and I'm sure we'll see improvements as things get prioritized. It's certainly not stopping me from playing a great game