This reminds me of Flask for Python (nb. although more is built in to Padrino, most of the functionality for Flask is provided by plugins). I've recently started using Flask for new projects in favor of Django. I feel that most of the libraries I use are framework agnostic, stuff like ORM (SqlAlchemy), PDF generation, redis/mongodb adapters etc, so being able to pick what fits and leave the cruft out is great.

But besides that, I feel that in recent times development is moving much more to the client - and client code like Javascript/CoffeeScript, Java for Android and Objective C, is getting much bigger at the expense of server side code. This is recently evidenced by the new 37signals Basecamp Next app which is 50/50 CoffeeScript/Ruby.

So the server side programming is on track to becoming "just" a API endpoint for all these different technologies and I think micro frameworks like Flask and Padrino are very well suited for that.