I've got about 175 hours so far. Granted, I've been playing other games as well. However, 175 hours is more than enough time to beat the main quest twice, do all the other questlines once, and do lots and lots of the side quests.
However, like Oblivion, I plan on doing all the questlines several different times. Except maybe the companions questline, that was just boring and irritating.
Edit: @The guy above me. You mean, go out and live in the real world? Psh, I'd rather be Dovahkiin than a regular jackoff any day.