My take on the BC (after doing a split stay at BC and Poly last December):
Rooms did show a bit of normal wear and tear (most noticably in the bathroom) but not enough to detract at all from the experience (overall, I really like the feel of the decor of the BC rooms).
I didn't like the ambiance of the resort as much as the Poly. While I find the theming attractive, it isn't as relaxing or enveloping. I also thought the resort seemed more chaotic (especially BC Markeplace in the morning) and the average guest more pushy and rude.
SAB, while really cool, is, IMO, too big for its own good. For example, I didn't like having to walk outside of the the pool area to get on the water slide. On the other hand, the CMs at the pool were wonderful, especially the guy doing the music/games for the kids in the afternoon (keep in mind, this was in early December when the pool is less busy).
As others have stated, if you like Epcot and DHS, the location of the resort is its biggest selling point. The advantage of being less than a 10 minute walk from World Showcase cannot be understated, especially after Illuminations. Being within walking distance of the Boardwalk is also very nice.
We're also big fans of the Cape May breakfast and it's great to be able to get to this so conveniently.
Overall, I like the BC as a home base for my EP and HS days on a split stay (or if I were on a trip where I was only visiting those parks). Not sure if I'd ever book it for an entire vacation, especially if I planned to spend multiple days at MK (there are at least 3 or 4 other resorts that I think have better ambiance/theming and better transportation to MK and/or AK).