Of course you'll see lots of IO. An application without side effects is rather useless.

Don Stewart has given possibly the best answer to this question on StackOverflow: http://stackoverflow.com/questions/6398996/good-haskell-sour...

Thanks, I almost lost hope that I will get a sensible answer. I don't buy the argument that real world code cannot be pretty; what would be the reason to use Haskell, then?

Bangs are well written and idiomatic Haskell code. Haskell is a default-lazy language. Good code uses lazy algorithms (to avoid wasted work) and strict data structures (to avoid space leaks), so efficient data structures need the bangs.

Real-world code (which is what most projects consist of) is rarely fully idiomatic and well-written, because it contains fixes to weird edge cases only some users experience, performance optimisations and such.

You mean production code doesn't look as pretty and toy code. Production code that performs well is well written and idiomatic if it follows the common practices of production code.