"really cool and useful to the average programmer" is pretty vague and hard to answer. But I'd say that it absolutely does. Namely the ability to build things with less code and have them be MUCH more maintainable in the long run because of strong static types and purity.
Case in point: one company ported a 43k line Groovy app to 8200 lines of Haskell [1]. The resulting Haskell app also was at least 64x faster and eliminated a number of major bugs with the Groovy system. If that's not "really cool and useful to the average programmer", then I don't know what is.
But this is just the tip of the iceberg. Haskell has an awesome library called diagrams [2] for the construction of declarative graphics. It can construct some impressively complex images with a remarkably small amount of code [3]. The pandoc universal document converter [4] is written in Haskell. There's also the classic paper comparing Haskell, Ada, C++, and Awk [5]. I'm sure there are other really cool and useful things that I'm forgetting.
Case in point: one company ported a 43k line Groovy app to 8200 lines of Haskell [1]. The resulting Haskell app also was at least 64x faster and eliminated a number of major bugs with the Groovy system. If that's not "really cool and useful to the average programmer", then I don't know what is.
But this is just the tip of the iceberg. Haskell has an awesome library called diagrams [2] for the construction of declarative graphics. It can construct some impressively complex images with a remarkably small amount of code [3]. The pandoc universal document converter [4] is written in Haskell. There's also the classic paper comparing Haskell, Ada, C++, and Awk [5]. I'm sure there are other really cool and useful things that I'm forgetting.
[1] https://www.youtube.com/watch?v=BveDrw9CwEg#t=1207
[2] https://www.youtube.com/watch?v=5_fCUSOn7m0
[3] http://projects.haskell.org/diagrams/gallery.html
[4] http://pandoc.org/
[5] http://haskell.cs.yale.edu/wp-content/uploads/2011/03/Haskel...