I've used BP with no ill effects but I get better mileage from Shell.
I have the Area451 cruise which I love. But with that or with the MDC, you'd have to do one hell of a lot of cruise controlled driving to recapture the cost. Actually, I doubt it would pay for itself over the life of the car unless you have a real lead foot and it's the only way you could control yourself.

That said, I still find that the cruise has already paid for itself in driving pleasure.