2 with bikes in comfort, no trouble
3 normal adults in 'comfort'
4 if one uses the sofa (i'd be OK on those sofas if I was tired enough, but I'm no giant)
5 if 3 are small kids! (hence the official limit)
5 if 400km into a Middle Road 600 (I was watching the Japanese GP over the road at the time - they TELL me they were sleeping ... ) - bikes downstairs, NOT in the room
More if, as above, and really desperate, and no snorers.
In case you haven't been in one, the rooms are NOT big - once all beds are deployed, there's not much room to manouevre!