Used to be a great shop at HEF. I used them to overhaul and repaint my tach, beautiful job. They also worked on my 8-day clock. A couple of years later I went back to them for some more work without having got the memo that they had been bought out by a sleezy 135 operator. Went in for an IFR/XPDR inspection. They pulled the altimeter and encoder out. They said my altimeter was no good, not even as core for an exchange (this was odd as it worked fine and it had been IFR certed every 24 months prior). Told them fine, but I need the plane, I'll just fly it VFR. They told me they wouldn't release the plane until it had a new transponder. Fine, get it done ASAP, but I want the core for my wife (Margy was running an aviation education program at the time and those sorts of things are great for that). Well, I pick up the plane and find they charged me to install the new altimeter in addition (didn't I already pay to have the old one put back in?) and the core had oddly disappeared.
Heard bad stories from other local opertors I trust. Posted a negative review on Airnav and Airnav allowed them to write a ghost written review impugning me. THat's when I lost faith in both the shop and the guys at airnav.
Always, always, get referrals, and make sure the shop hasn't changed hands since the referrers used it.