3 was pretty much a total rewrite of Rails, so you could argue that if you skipped 3 you are starting over from scratch. Pretty much everything changed apart from the higher-level concepts (even the opinionated stuff was diluted to a point)
Agree, Rails 3 absorbing merbisms introduced flexibility to the existing conventions making it easy to stray from the opinionated stuff. Rails 3 was still Rails but definitely made it easier to get yourself into trouble. And definitely changes any Rails 2 developer would have to learn.
I’ve experimented with most of the alternative frameworks and micro-frameworks. I have a real fondness for Sinatra. I’m happy most modern languages have their own Sinatra but I’m sad that most modern languages lack their own Rails.
