I'm undoubtedly a Haskell convert (from Erlang / Scheme / Python) with little experience in Go.

The investment is pretty big, yes, but I also believe it is great from a commercial perspective because it really improves the result for End-Goal-Programming (end goal is to serve business needs, not technology for technology's sake):

    1. Time to market for a product
    2. Easy / clean refactoring
    3. Massive scale code base management
    4. Program longevity and maintainability

1) Time to market is extremely important for businesses and products and schedule over-flow is a common problem in software engineering that Haskell really does help solve. Since building production software in Haskell I've become completely frustrated by Python because I spend far more time building in it due to debugging my own undisciplined habits out of the end product. I'm not a very disciplined dynamic type programmer.

It also produces cleaner and less buggy product for the end-user. Which is so important!!! Particularly as a startup.

2) If you need to cleanup some technical debt from taking short-cuts or not accurately pre-planning architecture, Haskell's type system makes it so friggin' easy your eyes will bleed when you try to do the same in a Python / Ruby / Erlang program.

Additionally, it really allows you to respond to the market better too! If you have to pivot your product it's not "Oh shit, now we're going to have to take that duct taped sewage monster and turn it into a duct taped ninja turtle." it's "Hmmm, well, let's think through the new types a little bit and re-shape some of this code, I know the compiler will tell me when I'm being a silly human."

3. Python and Ruby aren't really appropriate for large scale code bases because dynamic typing means you need an equally massive amount of tests to ensure no one else in the org fucks shit up. It makes team based programming on the same codebase far more manageable!!

4. Once I've built my Haskell programs and wrote a few minor property tests with QuickCheck, they usually run forever. I've rarely ever had a case where I would get unexpected crashes (usually from my not understanding Haskell's laziness earlier on in my Haskell career).

Long-term maintainability is massive factor here too; it's so much easier to figure out what the damn thing and all of its constituent pieces do with the type system!!! It's like having an index and a table of contents for a book. Since most programmers forget their own code anyway (comes back to that fallible human thing), having a neat and correct abstract description of your program and its parts is invaluable to a commercial enterprise.

So, in short, I actually think Haskell is the best language a commercial enterprise could choose. All you need too is one really good programmer that can mentor, then train them as you go; the good news with Haskell is even when you write shitty Haskell code (un-idiomatic, mostly in the IO monad, and barring space leaks), it's usually better than even the good Python and Ruby code those people would be writing.