One thing I've found interesting in my very limited experience of Haskell is the connection to formally verifiable properties. Programs written in C or assembly very often have correctness and safety problems—among many others, memory corruption problems. Haskell and many related systems help provide tools to check programmatically that various large classes of error condition can't be present in a code base.

You might think that this isn't worth the mathematical rigamarole that comes with it and that it's grown up with, but as people have seen in a number of other HN threads, formal methods are having a renaissance now and the tools we have that engage with them can get us a lot further than they could in the 1960s.

I have written many bugs, of many different kinds, in other languages that could have been detected automatically by a type system like Haskell's. I'm not suggesting that that makes the other languages inherently bad, or that other programmers (or I) couldn't adopt other methods that would also help avoid these errors, but I think the ease with which Haskell's approach can do it is something interesting to consider.