In my several hundred Choice stays, not many stick out in my mind, but a few have. In general, I agree that Sleeps are the most consistent and that "Qualities" can be some of the worst.
The Worst
Quality Inn- San Angelo, TX: I had to change rooms 4 times to get one without a 1/2" gap under the door and various and sundry insects flying about. I have stayed in cleaner places for $5 in El Salvador.
Clarion- Albany, NY: This is a 10 or so storey building with a motor-lodge attached to the back. The lobby is decent, but the rooms are hoorendously bad, and the neighbourhood is fairly dodgy, as this is in Albany.
Comfort Inn- STL: This was a Doubletree up until a couple of years ago. I don't think any maintenance has been done since the mid-80s.
Quality Inn- Montgomery, AL (South): A nasty old motor-lodge in a bad part of town. The Hampton a couple of miles up the road is cheaper and far nicer.
The Best
Clarion- PDX: New and very close to PDX. A restaurant would be nice, but the hotel still smeels new and the staff was very pleasant.
Clarion- Montreal, QC (Ste. Catherine): It looks like this used to be an apartment complex, and, consequently, all of the rooms are suites and fully equipped as such. It's slightly dated, but if you get a room on the 15th storey or above, the views are great. The biggest downside is that the closest parking garage is 3 blocks away and is pricey.
I'm staying almost exclusively in Hilton properties now, as my new corporate overlord has a contract with them. I can't really say that I miss anything other than the ease of turning points into miles.