The UI is good looking and sleek, but it is not fast by any stretch of the imagination. I mean honestly, I don't even understand how someone could have that opinion seriously. It takes numerous actions to get to things that should be one button press away.
It's light-years ahead of say for example, Oblivion's confusing clickfest of a pathetic excuse of a UI.
Skyrim, everything is but a few clicks a way in an easy well structured good looking way. I could
see a few small improvements being made as smaller font in the item list so more items visible at
the same time. Just minor stuff like that. No major/deep changes in functionality or design though.