I don't refactor with fear in my Rails apps since they have pretty good test coverage. I'm not saying it's perfect, but I've never had slow development because I wanted to refactor in this context.

It's been slower for me, personally. I write half the tests in Haskell than I had to in Python which means less updating of tests as requirements change. It won't feel slow to you until you've written productive (beyond beginner) software in Haskell.