I'm making headway in the main story now (Blades) because I'm in much the same situation. I have other stuff I want to play and I'd like to come back to it again with a completely different character. Level 32 and I'd been avoiding doing the main questline.
I'm constantly amazed at how varied and detailed all the dungeons are - it's a quantum leap away from Oblivion and it's generic copy & paste ones!
Not really. As far as the appearance goes there aren't that many to choose from. Its mostly just Dwemer, Ancient Nord and Caves. I think there are just more unique sections and more generic pieces that make them up so it doesn't look as copy/pasted, but you can clearly see some dungeons which use blatantly copy/pasted sections from tell-tale signs like openings that are clearly doorways but have been walled up a metre in.