Comment by thibaut_barrere

I think Heroku is not so much about Rails than about Ruby. You can use any rack-based app here, as well as host long-running job workers.

In the non-startup enterprises (I work with those), the work is usually to glue things together. Call a legacy web-service here, run a worker there, put things back into a legacy CRM etc. Ruby is perfect for that.

JRuby is even better, actually, and I wouldn't be surprised to see Heroku support it later on.