I was really disappointed by Haskell when I wrote the simple dynamic programming solution to the knapsack problem in it. To get good performance out of that too

I was really disappointed by Haskell when I wrote the simple dynamic programming solution to the knapsack problem in it. To get good performance out of that took a lot of time and help from people at #haskell to deal with space leaks. Ultimately, the functional solution was verbose, harder to understand and still slower than the more imperative solutions in Clojure (also very hard to get good performance in BTW, but at least you can easily implement performance critical stuff in Java) and Ruby. That experience really turned me off Haskell.