I think you must have missed the point somewhere. Test coverage and metrics are important not just to catch "programming" errors but also logical and semantic errors. Haskell only partially helps with those other categories.
I think that if you know how to use it, Haskell's type system can reduce your bug count substantially. It makes a difference, spending 30% of your time debugging as opposed to 70%. (These numbers are approximate and vary depending on the problem you're working on.) You still need to test, though. That is true. QuickCheck does a lot for that.
