I am currently on a really good healthcare plan with my wife's employer (large state university) after we got married last year. I'm based in Texas, so YMMV depending on your state.
Prior to that, I was on an ACA plan since they were first available, and before that on an individual policy. Despite its issues, I am a huge proponent of the ACA—I would not have been able to continue being self-employed and have reasonable access to healthcare without it. I am dreading seeing just how bad the Republicans screw up its core tenets regarding preexisting conditions (my wife is a cancer survivor) and subsidized access for the working class and poor (I made too much to qualify for subsidies, which doesn't bother me, but I've seen how much they help others.)
My silver plan in TX was pretty good—the network was a little smaller than I'd like but I was able to work with it. Last year I paid about 575/mo for that, which covered my son and I, and an additional 35/mo for dental. Deductible was about 1800 per individual, IIRC, with $10/35 copays for PCP and specialists. RX was a tiered plan with copays of $10/30/50/20% depending on the drug—most of mine were either $10 or $30.
My insurer (Aetna) pulled out of TX this year, but I don't buy the market-was-failing argument—it was pure retaliation for a rejected merger between Aetna and Humana.
Having had an individual policy for years before the ACA was available, it really was a night and day difference. Getting individual insurance was 3-6 months worth of tracking down medical records, dealing with hours of phone calls to explain why I didn't provide whole pages worth of details about medical visits I barely remember having (do you remember every doctors visit for flu or minor injury for the last ten years? I sure as hell don't.) I am dreading going back to that after the GOP finishes screwing this up.
If you're considering going off a group plan, I'd consider carefully whether you want to do that until the healthcare law is settled, if you have a choice. My guess is that what's going to happen is that preexisting conditions will still not be grounds for rejection but your rates will skyrocket for them, and the GOP will scrap requirements for minimum coverage, mental health, maternity, and preventative care benefits. The only thing I've seen that I think would be a net benefit is making HSAs available regardless of whether the plan is a HDHP, but I'm betting that all individual plans are going to either be an HMO/ACO or HDHP—PPOs will only be something you can get from a large employer. Your costs for what you do get are going to go way up.
When you leave your employer now, provided you do it before the ACA marketplaces are scrapped, you'll have about 30 days to get a new plan through a marketplace because of a life-change event, so you should do your homework ahead of time and pull the trigger on that as soon as you give notice. (The ACA actually gives you something like 60 days, but I think the Trump administration reduced that window as soon as they could, trying to cripple the marketplace even further.) The plan should be in effect until the end of the year, but all bets are off for 2018.
I'm normally the first one to cheerlead for going on your own, but I'd really consider that move carefully right now.