It's just as comfortable as the stationary bed. Like cmoliver said, the mattresses are identical. You may even find it more comfortable due to less usage. It is very easy to open and close. My son had no problems opening and closing it on his own during our last 2 stays at 10 and 11 years old.
As for mousekeeping leaving it down or closing it, that just depends on who is servicing your room. We've had both happen. We generally found that if we left anything on the bed, like a blanket or plush, they would make the bed but leave it in the down position. If we left it clear of personal items they would make it and put it up.