I used the Groupon for a basic bike tuneup here. They did a very thorough job cleaning my bike (do a lot of biking in the rain), calibrating the brakes, and fixing some shifting issues. These guys are top notch.. in fact they did a MUCH better job tuning up my bike than the trek store in north Charlotte.
The guys are super friendly and eager to answer any questions. You can tell they take a lot of pride in their work.
Only reason why I'm taking off a star is its a little pricey. Had both of my brake pads replaced and they charged me $40 bucks for the parts/labor. If I had known it costed that much, I would've done it myself.