Right, what bugs me the most about EQ2?
Plenty of things... hrmmm...
Specifically, off the top of my head, the tradeskilling interface.
Moving the camera, chatting, or doing anything outside the tradeskilling window causes it to become 'inactive'. So while crafting, if you move the camera or start chat, you have to click on the tradeskill window again to be able to use the abilities and counter the disaster events.
For something as repetitive and dull as tradeskilling, I think it would be a good idea to give more leeway for distractions such as chat or the in-game browser. It's not like there's anything interesting going on anyway... you're just standing idle with one animation and pushing buttons to whatever 'simon says'.
Also, beyond that little pet peeve; provisioners need something more than 2-6 recipes per level, adventure classes need a severe balance pass, the graphics engine needs to be revamped to make more liberal use of the GPU... blah blah blah, etc. etc. etc...