[vmchale]

> complicates debugging and performance reasoning

Lots of people say this, very few understand what it actually means and how to do the analyses.

> Laziness is, in my opinion, the wrong default.

Unfortunately, GHC is still the only compiler with first-class support for laziness as well as strictness. And you need both if you want to be able to do immutable functional programming.

But in the grand scheme of things it doesn't really matter if you know what you're doing when you use data structures. Some data structures are meant to be strict, others lazy. Haskell allows you to create data structures that are strict in the right places fairly cheaply.