Recently evaluated Fly.io for a company project but decided against it. I get the vibe that it fits the hobby/side project market more and that they're still in startup mode.
The reason to like fly is you get a 20-ish line yaml file that replaces (and I'm not exaggerating) thousands of lines of cloudformation. It automagically sets up the equivalent of a load balancer, autoscaling group, VPCs, db, vpn, etc. And it's trivial to replicate that environment per employee.
Plus the autoscaling using their firecracker stuff is fast.
I'd recommend most companies who aren't using tons of aws services take a hard look at fly.