Perhaps it's better now that the api has stabilized a bit. I've been using node.js & some Sinatra lately.

Upgrades tend to be smoother & due to less monolithic libraries. Also, the app startup time & TDD cycle tends to be faster with slimmer libraries.

It's also nice to be close to http vs the ambiguous controller methods & complicated route files.

Plus ActiveRecord is slow, especially with collections. The business logic can often be implemented in simple functions, resulting is less abstraction overhead.