Bugs are one thing that you'd probably know. But i think perk trees are flawed and many aspects of the game are imbalanced. I dont think Bethesda did enough play-testing. The quests are lacking and so is the amount of monsters ingame. Bethesda could easily have made mounted combat or an Interesting civil war or spears or crossbows or more post proccessing effects or animation improvements or decent ai or optimisations or.. the list is endless of what skyrim COULD have been, given maybe a few months.