I agree. It helps to have something tangible and to refactor later. I think the main issue that some people (myself included of course) have with that is refactoring too late. You never want to build something big on top of sketchy code. I've done this a few times myself to try to meet a deadline, and it's really bit me in the ass. We're talking weeks maybe months down the drain.

"Sketching in code" is a great analogy. Similar to how you'd trim off the rough edges in a sketched drawing, I've found myself cutting a lot of cruft when refactoring.