What people are saying is truth. He well not honor your Groupon, makes you feel he's doing you a favor for showing up. If you don't show up in a good mood he well tell you to shove it after you waited weeks to finally meet up. He tells you it's his rite to reject service to anyone, that's all good and dandy if the customer has not paid yet. But if you paid he should honor it period. Couldn't tell you about his work since I never got anything done. He has no office, no real shop, looks like he uses a buddy to do the work.
Remember that Seinfeld episode with the soup nazi !! That's how you treat this guy. You wait in line and don't say anything to hurt his feelings and maybe then you can get some service.
Luckily Groupon refunded me after I told them the story ..