The residence Inn by the Ontario Airport was the last hotel in which we stayed after an 8 week tour thru western Canada and parts of the USA. Expecting a large hotel building since this was a "Marriott", we were a little surprised upon arrival to find what appeared to be a California Apartment Complex with a number of separate buildings. So do not expect to find a tall building with a huge marble floored lobby with fountains. Do expect, however, to find some very nice rooms, and a staff that you would not trade off for anyone.
Our room was near the back of the property, and outside you could still hear the traffic on Interstate 10, air traffic at the airport of course, and the hum of the AC units from the various buildings. Inside though, our room was nice and quite. The wooden structures are well insulated against noise, and the So Cal heat. Our room was a double with a complete kitchen, and a nice living area, a nice plus if you are going to be staying here for a number of days.
A big plus at this location though, is the great buffet breakfast, which is included in the price, and a nice spread of hot and cold snacks at happy hour, which could double as dinner for many people. The other plus is the staff, which is very zealous in assisting their guests. We had to leave before sunrise to fly out, and it was hard to get a hand on a suitcase in the lobby, or getting in or out of the hotel van which took us to the air terminal.
I recommend this Inn and will be a return guest next time I travel thru Ontario, CA.