Now this is obviously someone who already knows what each quest is; the location and what to do, so for all of us that haven't played the game yet will definately take longer as we will want to soak up all of the information.
Now for those that think this means the MQ will be really short; the fastest Oblivion was completed in was about an hour so this sort of shows that Skyrim MQ will be twice as long as Oblivion which I think can only be a good thing...