I worked at the first one they did in SF. It's pretty insane, but if you're not put off by women running around, changing in the middle of the racks, and huge crowds, you can find some pretty good deals. I liked that they had a lot of accessories, as well as a large selection of designers. Let me know if you have any other questions!
I went to the first few BBB sales they had in New York, but I think the quality and selection of the merchandise offered has declined over the years. The deals used to be really good, but it seems with designers in New York having their own sample sales, BBB isn't as relevant as it used to be.
However, I do enjoy the early admission. If you can go on the first day there's free alcohol, which does make the shopping experience lots more fun.
i went to one in LA last year and was very disappointed. i know friends that have found great deals there, but i personally had no luck- it was really picked over and anything cute that i did find there was still really expensive. i might have just gone too late though. but i wouldn't go again, personally.
I went to one last summer here in Chicago. It wasn't that great. I bought a necklace and a ring though. Clothes-wise, it was horrible. It was like the leftovers from who knows when.