The graphics are simply horrible, but that is easily the worst part of the game (other than overpriced premium content).
I personally enjoy the quests, many find them boring but I don't know why. It may be due to the repetitiveness of the 'destroy the base' formula, but what else can you expect from a game like AoEO. One thing that does deeply annoy me however is the lack of random map mode, even with premium. The only other age game I've ever played is age of mythology and the best bits about that were the editor (not in the game) and random map (not in the game). I only hope we will get these modes in the future.