I’ve had an Ergomo since January that I bought used. It was fantastically consistent for the 1st 4 months that I had it. Then the offset #'s starting drifting (they had been very stable for the first 4 months). Nelson at Gita immediately replaced the BB (I had one of the 1st ones, and he said that some early units had a problem with the sensors loosening. The customer service at Gita was great; I had a new BB the next day. I’ve also checked the power readings that I get on the Ergomo against analytic cycling on climbs and they’re consistently within 1-2% of what analytic cycling predicts.
I have no basis for comparison, since I’ve never used another power meter, but I love the Ergomo. I use cycling peaks and I think the electronics on the Ergomo are far better than anyone elses. It’s great to see NP, TSS, etc. right on the unit, and their new firmware lets you customize the screen as you like it - try that with any other power meter. I liked it enough that I just bought a 2nd BB for my road bike.