This past December we stayed 2 nights at RPR then switched over to VWL for 5 nights and then spent the last ight at the Poly. My husband had never stayed there before and wanted to give it a try.
We were so unimpressed with the Poly. While it was nice having the monorail for easy transportation, the hotel room left much to be desired. It was a very large room, but very stark. Minimal decorations, yucky drapes, it was actually depressing to me. As was metioned above, there are separate bulidings, so you must walk outside to get anywhere.
RPR was pretty nice. Of the 3 USF hotels, it is our least favorite, but we did like it much better than Poly. The rooms are smaller. But they are well themed and we prefer the indoor corridors. The lobby at RPR was nicer than Poly's. Hope this helps without casting too much negative on Poly.