I'll admit there is some notable lag to the UI and game in general, but mostly it stems from the poor UI layout. I would imagine I have an above average computer, with above average internet access, and there is still notable lag with certain interfaces. As you mentioned, there is a tremendous amount of redundancy in having to drill through multiple menus to accomplish seemingly simple tasks. The worst menu lag I've noticed is with equipping skills, I don't seem to have the mouse scroll delay that most others are experiencing.
My most personal dislike with the UI is with trying to sell items.. It seriously feels like it takes 10+ minutes just to sell of random loot from grinding.. now that's excessive. But most notably is the obvious combat command delay.. Maybe it's just me, but I feel like I'm playing a turn based rpg where I have to wait a couple seconds before the actions take effect. (Just close your eyes and imagine that's the feel SE really wanted us to experience the game)
I'm trying to be optimistic that most of these "lag" issues will be resolved upon release, but as far as the UI, it's really hard to imagine them changing much in the near future. My point being, I don't think I've ever played an mmorpg that significantly changed the UI from beta to commercial release. Unfortunately, I'm going to wager that we're stuck with this menu setup.
For reference, I'm running an i7-920 at 4.0ghz and a hd 5870 with 16mb/s internet. And no.. I'm not cancelling my preorder.. lolz
Edited, Sep 12th 2010 6:36am by zeruin