Dragon Age II is Shorter than Origins, Longer than Mass Effect

Mike Laidlaw gave exactly this comparison in the Dragon Age II live dev chat two weeks ago, but Dragon Age II's length is a topic of discussion again, so Laidlaw repeats the description in a recent roundtable interview.
During a roundtable interview, Laidlaw told PSU that the length of Dragon Age II's campaign will depend on how you play. (Take a look at how you play games,) he said, to determine how long the campaign will last. (I'd say it's a bit longer than Mass Effect but shorter than Origins.)

The original Dragon Age offered plenty of hours outside the main story. You could spend hours after hours performing side quests or looking for loot, and Dragon Age II will be no different.

(The game will take longer with side quests,) he said, adding that there are full boss level creatures tucked away off the main story. (At the same time, you can get through the story quite a bit faster because so much content is off to the side. Mileage will always very, just take your habits and extrapolate.)