I think dungeons can have some very good loot,like music disks.But yeah,I think they are too easy.
There should be larger dungeons,that spawn a lot of mobs and they would have traps.Larger dungeons would also have a lot more loot!
A problem is you can just break through the wall to get to them. The walls should be made out of obsidian so it's harder to get it.
All my suggestion starts at 18:43. Agree with Etho?
But moderately-larger dungeons and special dungeons would be a nice touch.