When I have used reverse bookings before, I also find it interesting how far some SP's are willing to travel!
I tend to avoid those bids as inevitably when it comes down to the exact logistics, they either try to bump the price for travel or simply don't turn up or back out at the last minute.
I've had some success on RB's though, I think it can be the best way of finding someone decent who is actually available to meet.
I've also had offers on them that are well underpriced compared to their usual rates. I was once offered two hours for the price of 1 (£180 total) and another SP agreed a 2 hour rate at £250 when her 2 hour rate was usually £400! The meet never happened sadly but still interesting.