As Brian points out :
In terms of the Gartner Hype Cycle, Ruby and Rails are nearing the end of the "Peak of Inflated Expectations" and are moving into the "Trough of Disillusionment".
It's indeed true that Rails have enjoyed the limelight of being the darling of the community and a promise (or panacea) to put an end to the verbosity and *inelegance* of Java based Web development. It has been quite some time though, yet we hear people like Obie utter the following in the context of choosing Java over Rails in developing Big Enterprise Applications :
Like Gavin pointed out, you can't do an app with thousands of model classes in Rails. Okay, but I'm really not trying to say that you should try. Right now, I personally have no interest in working on those kinds of monstrosities, but to each his own. If that big enterprise application exposed web interfaces, I might be inclined to use JRuby on Rails to do those..
It's time to deliver for Rails ! How long will Rails shrug away from the enterprise applications branding them as monstrous ? It's time to take Rails out of the playful scaffolding model that delivers basic CRUD applications at lightening speed. To deliver complex enterprise applications, you need a performant application server with production quality deployment support, a real fast virtual machine and solid domain modeling capabilities. We all know the ActiveRecord model is never going to scale up for large complex domain models. The Rails community, till now, do not acknowledge how important it is to have a separate domain model, decoupled (or loosely coupled) with the persistence layer. And ActiveRecord will never take you towards that end. How much strong metaprogramming capabilities you may use to offer fancy dynamic finders in Rails, ultimately you need to have a strong decoupled domain model to deliver big enterprise applications. Till then, I guess, JRuby will be your best bet and Rails will remain just another Java library sucked up within a Java application server.