I don't have anything running in production with now, but it has been great for quickly deploying experiments/ demos. The only problem I have with it is that deployments sleep after ~1 hour of no traffic. When requesting a site that's sleeping, it takes up to 20 seconds for it to respond.
To solve this issue, it's possible to setup a cronjob that pings the site every hour or so, to keep it alive. But it feels rather devious.
Have you been interested in switching to now?