I've been using One Medical for I think like 8 years now, at first I paid for it myself but the past few years it's been paid by my employer. In my experience they're still a bit more convenient than the average medical practice. At least I don't have to play phone tag to make an appointment, or have my appointment canceled because I was busy and couldn't answer a confirmation phone call. That just speaks to how terrible the average medical practice is at customer service.
But I feel like One Medical has already started declining in quality and reverting to the mean of other providers. It's no longer easy to find an open time slot, I had to schedule my last physical a month and a half in advance. Last time I tried to do a teledoc session which is advertised as a 24/7 service, they happened to be closed all weekend (I'm not sure if that was a very unlucky one-time thing or how often that happens). Like with many other VC-funded companies, the early user-friendly imbalance of supply & demand was never going to be sustainable as they scaled up.
What I have hated to see most, though, is how they have maneuvered their way into being yet another employer-funded health benefit. Now that it's "free" for me, my bar for service quality is much lower than it was when I was paying $100 a year. I already hate that medical insurance is employer funded in the US - the best solution would probably be a European-style government funded system, but the second best solution would just be to ban employer-sponsored health plans and let companies pay those amounts directly to employees to let them choose their own plan. Right now we have the worst of all worlds, it's not universal and it's not market driven either. And One Medical is now just the latest example of a similar kind of crony capitalism, which was true before Amazon bought them and I'm sure will continue being true now.