Yeah, just test it against a few others... if it's off the average by a pound or two, I'd take a sharpie and write the error on the dial face.
If it's off by more than a few pounds, I'd buy a new one.
I had one of those AutoZone gauges that I used for years... until I found out that it was 6 pounds off. I bought a nice liquid filled unit with a self correcting diaphragm from
www.quickcar.net that I like a lot. They're about 40 bucks and pretty popular around the pits.
http://www.quickcar.net/tire_mgmt/lq_tire_ga.html