I've seen two ex track greyhounds try to work (on several occasions!) and both were diabolical in their obedience, had to be lifted over gates and ditches, had the turning circle of a bus and were the biggest canine whingers I've ever met!
Of course, you could put the time in to improve their obedience, jumping, etc, but if you're going to put the amount of time needed into a dog then you might as well get a pup!
My opinion: get an ex track greyhound as a pet or for breeding purposes, but not as a working dog!
Crow