It's a very intelligently-designed framework built on top of a very expressive (even fun) language. But some web apps are too trivial to justify the overhead,

It's a very intelligently-designed framework built on top of a very expressive (even fun) language. But some web apps are too trivial to justify the overhead, and some may be too vast to want to run in a somewhat pokey interpreted language. But for something of the size and complexity in the range of Basecamp or (one of my favorites) Snacksby, you'd be stupid not to use it (or a similarly-capable framework). Another seriously cool framework is Seaside, but so far I haven't gotten my hands dirty with coding, just played around with the seriously amazing dabble DB. It's not very "web like", but it can do stuff that makes my head hurt when thinking of programming it even on top of Rails.