I'm also a big fan of Kaiser, and can share a couple of anecdotes to illustrate why.
A few years ago when I was working for a startup and had insurance through United Healthcare, I came down with a high fever and then started seeing blood in my urine on a Saturday. My only option was to go to the ER, which I did.
In the ER I had blood and urine tests, which determined that I had an infection in my kidneys. I was treated with intravenous antibiotics, and sent home a couple hours later with prescriptions for a couple more drugs to take for the next week or two.
IIRC my total bill for the 2-3 hours I was there was around $6,000, of which my insurance covered about $1500 and I was left with a $4500 bill to cover out of pocket. I remember thinking at the time that such an event would be financially catastrophic for most people - I was fortunate that I could afford it.
My wife has been with Kaiser for many years. Last year my wife started experiencing chest pains, which turned out to be pulmonary embolisms (blood clots in the lungs). She was admitted to the ER as well, where they ran some tests and got her on blood thinners. This was followed up with lung capacity tests and a few other things. Like me, she was in the ER for just a few hours, then sent home with appointments for follow-ups.
Total cost for my wife was about $50 all-in.
The magic of Kaiser is that when the insurance and the provider are both the same company, there's no dispute over pricing. There are no fights over bills, and no surprise costs that weren't covered. We have deductibles with Kaiser, but almost all services are a low fixed cost, so we don't eat into those deductibles much at all. This is not the case with other insurance companies.
In my mind the Kaiser model is what the US should have as a national health care system, that's really good at covering the 95% cases at a reasonable cost, leaving people the option to go to other providers for specialty care if needed.