Hi,
I myself have a couple of sites deployed on heroku. [login to view URL], [login to view URL] to name a few. I have used CloudAMQP little lemur, pgbackups and a few other plugins. Also there is a tweak doing which I can save you on $34 for per dyno expenses, using two dynos one for worker(celery) and the other for web but both using the same postgres db. I would recommend using waitress-serve instead of gunicorn as waitress-serve is more stable and resilient compared to gunicorn. I develop on python+django and have used fabric for system deployments in lot of my projects. Quiet curious and unsure as why would you use fabric with heroku as its own deployment is so easy and robust. Let me know if you are interested in my assistance.