I tried Fly early. I was very excited about this service, but I've never had a worse hosting experience. So I left. Coincidentally I tried it again a few days ago. Surely things must be better. Nope. Auth issues in the CLI, frustrations deploying a Docker app to a Fly machine. I wouldn't recommend it to anyone.
I find their user experience to be exceptional. The only flake I’ve encountered is in uptime and general reliability of services I don’t interface with directly. They’ve done a stellar job on the stuff you actually deal with, but the glue holding your services together seems pretty wobbly.