DH and I have been with Caresource Marketplace plans since 2016. We've had Bronze HDHP plans except for one time when we had a Silver plan.
In our area, Summit County, Ohio (Akron area), we have a large selection of in-network doctors and hospitals, including Cleveland Clinic and all the smaller hospital systems that they have bought up in the last few years. One of the other large hospital systems is not in-network so we avoid that one but really have plenty of providers to choose from. But, anytime I start with a new provider I do call and verify.
We chose Caresource because their premium prices were the lowest of our choices at HealthCare.gov. The prices weren't just a little bit lower, they were a lot lower.
Claim wise, most claims get processed quickly, some take longer, but I have never had a claim denied. When I have needed to call them it takes a while to get through the robot menu but once you get past that they do answer questions and provide info. Most times I say something like, "Speak to a person" or Customer representative" and that gets me to a human.
We have been using their mail-order pharmacy services, which is currently CVS/Caremark which has been wonderful. Good prices and very fast mail order service. We always check with GoodRx or RXSaver to compare before ordering. We got a letter a few weeks ago that the mail order pharmacy for 2020 will be ExpressScripts. I don't know if that is just in Ohio or everywhere. Check that out. Many of our local neighborhood pharmacies are in-network.
I tried using their autopay plan (Instamed) a few years ago and found it unreliable so I just pay online manually. Their website is usable but not spectacular and they have a decent app. Our plan includes some rewards for doing preventative things, yearly exam, mammogram or PSA, etc and you get credited with rewards that can be used for gift cards. We used our $25 each rewards for Panera gift cards which was nice.
Overall our experience with Caresource has been positive and we've stayed with them year after year. That's mainly because of the premium rates but also because of the very large in-network provider list in our area. Check that out in your area.