I have a friend who is getting one soon. He has had his assessment appointment.
He has been almost completely deaf since birth, and has really bad hearing in one ear only. He is not moving from a particularly high base
His take at the moment is "I don't have much to lose". I guess it is a gamble, but as long as you go in with your eyes open...
Anyway, I will post back after he has it done, and let you know how it goes.