Can't comment on the length of the main quest because I've barely started that yet. However, what I can say is that I've racked up 49 hours so far in Skyrim, on one character, and there's still a metric ton of stuff to do.
As a result I'd hardly say the game was 'short', given how the main quest, whilst important, is not the sum of this game by any stretch of the imagination!
You are correct,by using tmm 1 and looking at all the areas to explore It looks like you could spend days on side quests,I only enjoy playing the Main Quest though.But if side quests are your thing then as you said you won't be dissappointed.
40 hours of main quests, and 400 hours of side quests. and i've played a total of 70 hours without barely doing the main quest. XD
i have to say. if you don't look at the journal, the main and side quest seems kinda seamless. i really can't see the difference between main quest and side's.
Skyrim rules <3 *nerdgasm*
When you finish Sovngarde you have completed the main storyline.