Heroku for X
Many new platforms state that they are simple 'Heroku for X' (replace X with PHP, Node.js, .Net, Java, ...). These platforms I feel are missing two key points that Heroku brings to the table: the server-less cloud and a growing platform.
First, Heroku is revolutionary in that there are no servers for you to worry
about. Several of these new 'Heroku for X' platforms spin up new servers which
ssh access to and can use how you will. But I don't want to worry
about this! Even if I say that I don't understand, I have always had
access therefore I need it. Go try Heroku, you won't come back and tell me the
same thing. A side effect is that the Heroku platform pushes you in a way to
build scalable apps. If you have access to a server, you probably won't be
The second is a growing platform. Node.js is far to young to warrant a hosted platform. Technologies like Java and .Net may already be to established. It may be difficult to change the direction of Java and .Net deployment. Rails is a growing platform. Granted it is smaller than Java or .Net, but it is far easier to convince a group of people who tend to be early adopters than those who have a general distrust of new technologies.
Heroku leads the way as a platform. It has revolutionary ideas in a young technology. Heroku is the gold standard, every other clone of Heroku has fallen short.