Everyone always says that, but I don't think it's a good intro :-) (e.g. I think the top comment in the lobste.rs thread is suffering from the type inference / functional bias, which is not necessarily due to TAPL, but it's a common thing I've noticed)

Right now I think Siek's book is better for what I want to do, though admittedly I didn't get that far into it, because my type checking project is way on the back burner

I would like to see any type checkers that people wrote after reading TAPL!