Very cool! Where do your servers run, and is there any callback planned in case your service gets discontinued?
I highly doubt the service will be discontinued ever since traction looks good and we have plenty of funding, but Gigalixir and Heroku are almost interchangeable. The only difference really is that Gigalixir doesn't require a Procfile. However, if you fallback to Heroku, you'll lose clustering, hot upgrades, etc.