I've been using Rails for a decade now, across many jobs, and one thing I've experienced fairly consistently is the worst Ruby web apps I have ever dealt with are the ones that weren't written in Rails. I've both seen and spent a lot of time rewriting overgrown Sinatra monstrosities with assorted non-AR ORMs. These apps were generally riddled with XSS since they didn't handle escaping correctly, often had unmaintaina…
I seriously would have gotten the job done in half the time, with less problems had I just used Rails...and I've written my own ORMs before - I have somewhat of a clue.