I agree.

I was introduced to Ruby through Sinatra. Developed all my web apps using that though I used to play around with Rails. I had an initial idea that Sinatra was meant for small apps, and for anything serious you should go Rails.

However that idea seems invalid now; the way I'm now used to Sinatra, it is kind of getting almost all the goodies of Rails without the Routing layer (which I find hard to follow - as mentioned by the OP).

Sinatra+ActiveRecord+ActionSupport+ActionView = Rails - Routing - ActionController

http://gist.github.com/423571