I'm 130 hours in and haven't done the MQ past High Hrothgar visit, the Thieves Guild, the Dark Brotherhood, haven't visited Dawnstar, Morthal or Riften yet, have only done 1/3rd of the Stormcloaks and none of the Imperials, also haven't done Bards College, Blades, Temple Quests......
This is my favorite Elder Scroll to date and I've played since Daggerfall. (Wasn't there one before that? Arena?)
I love the Dungeon Quests, the messengers.... in fact, I'll often think "They should have had a follow up quest to that..." and then THEY DO!

In fact, now that I "know" the game, I just started a fresh character for a complete playthrough - lol. Took 130 hours but now I'm looking forward to another 200 easy.
:) Love you Bethesda!!!!!! Without you my gaming shelf wouldn't be the same (fave games: Morrowind, Oblivion, Fallout 1,2,3, Fallout:NV, Arcanum, Shadow Magic, Jagged ALliance 2, Stalker: CoP, The Witcher, Baldur's Gate 2 - so Bethesday has 5 of my top ones!)
J