Auto-scaling is a killer feature, platforms like Heroku or DotCloud do not support this.
Can someone explain how this will work, and the pricing? It looks like it's a matter of setting "Instances" and "Connection Concurrency" but the docs are WIP (no explanation on how the latter is different from the first): http://docs.duostack.com/ruby/paid-features#pricing
This is how Google AppEngine does it (btw: you can do it with nginx + ngx_supervisord + supervisord).
On the other hand, if you want one platform for all your projects, whether they're Node, Ruby, Python or PHP apps... Then the choice is easier :)
