I've stayed there twice while attending conventions, both times with a group of teenagers. I've been impressed both times. We stayed because it was close-ish to the convention center. For me, the walk is doable, but when I come with my family, which includes a 3.5-year old, I prefer one of the closer Harbor hotels.
The first time, we stayed in the first building that backs up onto Katella, right behind the office. I know there was some road noise, because Katella is busy, but it didn't bother me or any of the kids. Those were queen-queen rooms, I think, and had the hardwood floors. Rooms were comfortable!
The second time, we stayed in Mission Suites. They were plenty big, and we LOVED the little room with the daybed. I would seriously consider staying there again as soon as my DD is old enough to do a little more walking.
I do think it may depend on what building you are in what your experience is. But we've been pleased both times!