You can't beat this place for location. It is literally kitty-corner to Belmont Park. You can walk to the "quiet" boardwalk and beach which are right behind the house, or you can walk a couple minutes to the "busy" boardwalk, grab a scooter, and take off to wherever you want to go. With free parking at the house and the scooters a measly $0.15/minute (and there's usually a few located within 20 steps of the place), there is absolutely no reason to drive anywhere in Mission Bay. The only reason to drive is if you're headed downtown or something.
The fine print (Which isn't so fine, since they're up-front about it in the posting): This place is small. We had two full size luggage bags and couldn't fit both of them in the bedroom and have the ability to close the door. We couldn't brush our teeth in the bathroom at the same time. I'm glad we didn't have to figure out how to get in the front door if we needed to open up the couch into a bed. But... we didn't spend much time inside! When you're in the middle of the action, you're there to play, right? Yes, the walls are thin. You'll hear the people next door, and the people on the roller coaster screaming until 10pm. But, if you go get in on all the action going on out there, you'll sleep like a baby through it all when you call it a night! When we wanted quiet, we went to the beach behind the house. There were very few people and calm water, but comfy sand and plenty of sun.
To recap: If you're looking for a spacious, quiet place, you may want to look elsewhere. But, we 100% recommend this place for it's location and proximity to... well, everything you could ever want to do, really. If/when we come back to Mission Bay someday, we would absolutely stay again!