I had a great result on my first RB and have never matched it since (still sleeping with the first WG on and off four years later though). RBs suffer from pretty much the list of problems that you have described - offers from out of area, WGs who haven't read the post or are asking for much higher fees, even a few fall throughs once the booking is set - time and date don't really seem to be that fixed which can be a problem from the POV of funds and schedules.
That said I would still recommend them if certain things are in place - if you are travelling to hotel in a strange place it can be an interesting way of getting an outcall. They suit people who are looking for something specific like anal, and who are prepared to pay. I get better responses when I put up £120-150 bids, and would doubtless attract still more attention with higher fee offers. Its a good way to pick up hotties for slightly less than their usual rate if you are lucky, though you can also end up looking at three profiles and agonising because you can only afford one.
Personally I now look at who bids, add ones I am interested in to a special AW hotlist and get back in touch when I am in the mood to meet them specifically.