Comment by geoffc
15 years ago
RoR for dynamic HTML apps used to be the coolest thing but now the really new/cool stuff is written as a JSON server talking to AJAX and mobile clients. In this world node.js, clojure and erlang (maybe) are cooler than RoR.
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.
Heroku is also planning on rolling out node.js support which will help round them out even further.
Entertaining, as a lot of Heroku's infrastructure is built on Erlang.
It's funny but just as backend platforms really started to get good all the action shifted back to the client.