1. INTERFACE FIX: the interface (menus, etc) are absolute shite. various problems include scroll wheel not working, mouse moving slow, text not highlighting, menus are a pain to navigate, etc. EDIT: this includes the skill trees, which are VERY hard to navigate
2. HOTKEYS: instead we have the "favorites" menu. i dunno about you, but having to open a menu every time i want to switch between sword, magic, or bow really kills the immersion. oblivion, fallout 3, and new vegas all had hotkeys. why fix what aint broke?
3. IMPROVED MAP: yes, the map LOOKS fantastic... but honestly it is a chore to navigate. there are bigger gripes, and it's not terrible, but it could use some tweaking. (why can't i zoom all the way out???)
4. BETTER JOURNAL SYSTEM: this may or may not even be possible... but why does the journal suck so bad?? except for the main quests, i can never tell where i'm supposed to go or who i'm looking for. there should also be some kind of quest log or something, so when i'm told an important (or unimportant) name/place, i can reference it and see what the name/place was. (example: it took me 2 hours to figure out who i could buy the house from in White Run, since i didn't immediately commit the NPC's name to memory).