It's really not. The people I play with are power gamers...hardcore playing around the clock. Normal people are mostly in their mid teens to early 20s. I'm prob just barely ahead of your average player since I've had rl stuff going on and havent clocked as many hours. Keep in mind the level cap is 80, unlike the 50 cap we're used to in most fledgling MMOs.
My friends also played BETA and knew the quests up to level 30 or so, which helps and is largely why they blew me away while I was trying to learn the controls. The learning curve will really slow new players down, but it isn't overly complicated once you get a feel for the controls.
The UI QUestion--
The UI can't be changed, so some people who are used to custom UIs aren't thrilled. The UI they provide is functional enough so far though. I haven't found a real good way to incoporate my G15 keyboard yet, but I did manage to download a profile that allows some G15 useage.
I would like to see them offer additional macro bars down the road, but other than that the UI they have implemented works just fine...for now at least. I haven't seen the raid UI yet so that will be something to look at down the road.