IME, KEH BGN stuff is hit or miss, to the point where I would probably avoid something of that grade in the future, especially a lens. I have been unhappy with BGN purchases several times (meaning that I thought it should have been labeled worse than bargain, but not badly enough to bother complaining and making a return). I have never once been unhappy with an EX or EX+ purchase.
They do have a good, hassle-free return policy, however, and I have only had good experiences with their customer service.
I think part of the problem is that BGN is sort of a "wide" grade. It takes a lot for KEH to call something worse than BGN, and a lot for KEH to call something better than BGN. Therefore, a lot of stuff that is not quite UG makes it, a lot of stuff that is not quite EX makes it, and a lot of stuff anywhere in between makes it. IMHO, the BGN category is really more like 60-84 percent, instead of the 70-80 percent that they state. I think EX is more like 85-95 percent, and EX+ is 95-98 percent.