It scales automaticaly, analyzing the resource you need on your server, and you only pay what you use, like electricity.
It supports actually PHP, Scala, Ruby, Java, Node JS, and it's still upgrading. Also they have deployed PostgreSQL, MySQL, CouchBase and they are working on MongoDB integration, and ElasticSearch as well.
This company is pretty young, so they have a good support, as they care for their customer. I don't hesitate to send them an email and then give a call, or to tweet their account. Usually I get an answer under 2 hours.
Short story: I used to work with Play 2.0 and MongoDB, and had several issues on Heroku because of a problem on their side with the MongoDB driver. They didn't help in 3 days. With Clever-Cloud, everything worked perfectly, and they even helped me to deploy my app the first time. I immediately migrated my apps from Heroku, no regrets since.