Did you manage to convert any to be regular customers ?
That's the crucial question!
My gut feeling is that anyone who jumps at these sort of offers is bound to be a one-off and even then I reckon the complaint ratio would rocket after the job's done.
I had Groupon phone me once. I said to the girl "So you get me customers who are going to pay half my normal rate, and then I have to give you half of that, so I get a quarter and then I have to scrub off umpteen years worth of dirt and then I never see them again?
And I would think that's a good idea because.........?"
End of conversation