I'm on the opposite side of the spectrum, I've had GlowShift Pyro, Trans Temp, Boost, and Fuel Pressure gauges for nearly two years and couldn't be happier. They all work like they should, report correct values, and I use the different colors more than I thought I would.
I had a problem with the fuel pressure gauge which might've been caused by me and even though it's out of warranty, they're taking care of me and repairing it now.
I need another set of gauges for my "new-to-me" truck and I'm definitely going back with GlowShift, they've earned my business. I've also recommended them to a few other folks, all of who have reported that they're working just fine 1-3 years later.