I have the Bester 500 and it makes a good jumping stone between the D8XX and 1000 grit stones. It also is good for significant rebevelling when you can trade some speed for a lot less scratches on the blade that may never go away with the D8XX, and also no need for an intermediate stone before hitting your 1K-1200 grit stones. In going to a Zero grind on a Endura it took about twice as long on the Bester as it did on the D8XX (it took about 15 minutes for one side on the Bester, and about 7 minutes for the other side on the D8XX), but on normal rebevelling the difference won't be that big. The edge it leaves is also not bad, as it seems finer than a DMT Coarse (as expected) but cuts way faster than the DMT Coarse.
That being said, if all you are doing is removing the D8XX scratches before you hit a finer grit and you aren't going to rebevel with it the Bester 700 has gotten rave reviews. I personally haven't used it, but a lot of people on foodieforums swear by it. I think it is a decent bit cheaper then the Bester 500, as well. I know for a fact that the Bester 500 takes a long time to soak and dishes very slowly, and have heard the same about the Bester 700.
Mike