I've only done the main quest to I think the 1/3 mark. And the main faction quest (meaning Legion or Stormcloak) to about the halfway point.
I haven't even done much in the way of other faction quests, since the Companions are bugged for me with the Hall not resetting after an attack on their HQ.
All I can say is... WOW! Every cave/fortress/dwemer ruin/etc. has a story... caves are definitely not samey-samey like Oblivion. I still have upteen sidequests unfulfilled, and countless Misc. Ones. Whole swaths of Skyrim are almost entirely still unexplored.
Seriously, the best aspect of the game so far is the background that accompanies almost every location. Hardly a 'dungeon' exists that doesn't have a narrative of some kind, rather than "Here's a randomish cave filled with rats/goblins/etc." like most RPGs. Each one seems to have something that makes it unique. You don't just rush through them to get them "Out of the way". To say that almost 80 hours in is a pretty big deal.
Also thanks for putting the exits near the end point, or a shortcut back to the front. Saves countless hours of tedium walking back through an already cleared area.
In short, everything is fun, and 'drag' moments - the times you say to yourself, "I have to clear this/do this, boring stuff to get to the good stuff." is minimal.
Thank you so much Bethesda! I'm almost scared about the DLC. This is like pre Civ-5 action, "just one more turn" = "Just one more quest".
My only complaint is that I had to sit through the Twilight Movie to get wife credit for playing Skyrim all last weekend.