Move Over Rails. Here Comes Merb. : Page 5

The techniques I discussed in this article (note that I did not cover using page and fragment caching, testing frameworks, and "slices") reflect my own use of Merb to create small, targeted web services and web applications. I believe that Merb is an especially good fit for writing web services; notice that when you create a new resource with merb-gen, the generated controller contains a commented out line that you can uncomment to enable rendering XML, YAML, and JSON:

class Feeds < Application
  # provides :xml, :yaml, :js

When you use a provides method call in your controller, you get an automated conversion of Ruby model objects to data formats, which are also useful for implementing web services.

I am still experimenting with Merb to understand which other kinds of projects are a good fit for it and which are best implemented in Rails. I encourage you to do that same.