we had an autometer oil filled boost guage on my FC, and we could *see* for a fact that it was giving incorrect readings by over 2 or 3 psi, as we had the Microtech MT8 Handset to corroborate its testimony.
just to be sure we also hooked up an RE Amemiya boost guage, and then a Nizmo boost guage, both of which corroborated the reading the MT8 handset was giving us, and not the autometer boost guage.
i think they are so popular not for any quality reasons, just b/c they are so available, and so shiny and trendy.
i wouldn't have on in my car. I swapped mine for a crappy rear wing for a 1st gen RX7. I still figure i got the good deal.

you get what you pay for.