I am intrigued by this approach (I have Structure and Interpretation of Classical Mechanics on my lengthy to-read pile) but I do wonder whether expecting ~sophomores to be trying to pick up Haskell and the physics at the same time is a bit much.

The aspect of this that interests me most is related to a classic observation that, for most people learning physics, it's hard to separate difficulties with the physical content and difficulties with the mathematical content. The distinction between these is vague, but the separations like "set up the differential equation" vs. "solve the differential equation" that this functional style suggests seem like a good approximation to "physics" vs. "math."