I got this working fine except I don't get any logging for the actual app that's running. It tells the the app has booted and then nothing.
* Directory for apps: /Users/gary/.puma-dev
* Domains: dev
* DNS Server port: 9253
* HTTP Server port: inherited from launchd
* HTTPS Server port: inherited from launchd
! Puma dev listening on http and https
Without being able to see the logging output it's not usable for me, which sucks because this seems rather nice.
Edit: turnning on debug mode shows minimal logging. Still haven't found how to enable full development logging.