Got a class or model that’s getting a little too fat? Refactor to Modules. I’ve done this a few times lately, and I’ve always liked the results. Easier to test, easier to understand, smaller files. As long as you’ve got a tool like ctags to help you navigate between methods, there’s no indirection penalty either.

That said, I’ve seen code that is overmodule’d. But, that almost always goes along with odd callback structures that obscure the flow-of-control. As long as you stick to Ruby’s method lookup semantics, it’s smooth sailing.