Had three experiences with JLCPCB.
When it goes well with no problems, it’s fast and cheap. When it goes awry it’s painful.
First one was a personal job for myself, and it was great - everything went OK.
Second time was when I tried to use them for work - they emailed me back to say the Gerbers weren’t in the right format. There seemed to be significant communication difficulties in getting this resolved and we went around in circles, so the order was cancelled and we went with a UK based supplier. Oddly two weeks later the PCBs turned up.
Third time was also for work, and there was a problem with the credit card being charged but the PCBs never showed up and they cancelled the order. From what I could tell it was another issue with file checking. We struggled to get an understanding and a refund.
I’d probably try them again for a non-work related job, but I’d ensure that I pay using a method that has some kind of protection in case it goes wrong.