Rachel & Grace's place is far more spacious than the pictures can convey. We would definitely stay again!
However, I do want to mention a couple of things for future travellers to be aware of. There is an air conditioner in the main room but nowhere else in the apartment. It was pretty hot the first couple of nights, but what can you do? It's Seattle in July! The air conditioner cools the main room very well though, but getting nighttime cool air into the bedrooms was difficult (even with the fans provided and the windows open).
Being a non-city girl, I found it very difficult to sleep with the highway noise so close. I tried to pretend it was white noise, but I'm so used to quiet! I think the room with the twin beds in it was a bit quieter based on its location in the apartment (I was in the Master).
Overall though, you can't beat its location. It's an incredibly easy walk to the convention center (though I was at the Hyatt regency for my conference, still an easy walk). I surprisingly felt very safe as well and had to do at least one nighttime walk on my own.