Mumof2, like has been said, the Universal hotels perks are way superior to Disney. We have always checked in around 8.30 - 9.00 am. If our room has not been ready, you get your "room" key card, they look after all your luggage (and have a front office safe for passports, money etc). You just walk over to the parks and enjoy your first day. When you get back, you call housekeeping from the lobby phone and they give you your room number, your room key card is already programmed by then so up you go.
On your last day, your card is valid for the whole of the day, until when the parks close.
This also is relevant if you use the hotel's car park - you can come and go. One year we had a problem, but just explained we had been staying to the car park security guy and he let us in - and we didn't have to pay for parking, either.
Enjoy, it's a great experience.