We considered moving onto Fly since we were transitioning away from Heroku. We ultimately decided on just AWS for our core products and digital ocean app engine for smaller experiments.
Fly's overall experience wasn't as smooth as Heroku, from the dashboards to the weird errors for technical things that should work but didn't. The logging and error handling wasn't as informative as it should be. In essence we agreed with the value proposition of "give us PaaS magic with more control over the infrastructure than Heroku" but it wasn't sufficiently magical. The whole low-latency cdn-like distribution angle wasn't really relevant to our use-case.
Fly's overall experience wasn't as smooth as Heroku, from the dashboards to the weird errors for technical things that should work but didn't. The logging and error handling wasn't as informative as it should be. In essence we agreed with the value proposition of "give us PaaS magic with more control over the infrastructure than Heroku" but it wasn't sufficiently magical. The whole low-latency cdn-like distribution angle wasn't really relevant to our use-case.