What it comes down to is that Haskell's type system eliminates whole categories of bugs because of the language. Having the correct way to use the language outside of the language itself, as an addition, in the case of Python or Ruby or (insert interpreted language here) makes for lots of extra debugging time.
When you use a programming language, you use its ecosystem. Haskell has its own tools and norms outside "the language itself" which I am obligated to take advantage of. If I develop software in Haskell, but completely ignore these tools, and make complaints which have DIRECTLY to do with my non-use of available facilities, I do not then have the right to say that Haskell is broken and objectively worse than language X. It does not follow.
Writing unit tests is not hard. Nor is it rare or exceptional. Wrestling Haskell's type system is not necessarily easy. Overall, making programs do the right thing is a big problem in any language, including Haskell, and one hopes that any system of significant size is being tested properly whether it uses a static type system or not.
The use of a type system is not in itself an objective slam dunk for Haskell over Python or anything else.
Have you coded in haskell? Really, the great-grandfather post that provoked this wasn't an attack on python, it's pointing out a difference between the type systems in ML, haskell, scala, and maybe typed racket, of the non-dependently type languages vs. all others.
I use Python + Pyramid daily; and I love it. However, I love Haskell more. Yesod/Snap/Happstack have quite a ways to go before they are on-par community and feature wise with Pyramid/Django/Rails/etc... but it's mature enough for production use.
With a little extra learning curve; it beats the pants off of Python + Pyramid + unit tests and lots of extra debugging time.
