RoR is the cat's meow, right? So it follows that apps created using it will prove the point.
Maybe someone from Twitter has written an article describing their experiences?
- One exemplar that comes to mind is SimpleLog, "[A] simple Ruby on Rails weblog application with support for comments, tagging, archiving and quick-search. It features a simple admin section with authentication and a focus on writing over all else." (from the SimpleLog Wiki)