Padrino creates a rails like structure around sinatra. It provides convenience scripts, helper methods and some glue code to create rails style apps. If you like sinatra but want more structure around it you should definitely checkout Padrino.

I was considering Rails for a project but considered it overkill for my needs (small RESTful web service). I discovered Sinatra and fell in love. Then I discovered I could get the benefits of Sinatra, with a bit of Rail-like "magic" (helpers, ORM support, generators, migrations) by using Padrino. For me it's a perfect fit.