&quot;My book&quot; doesn&#x27;t tell what&#x27;s bad, but things like how the  community surrounding a tool is. You can&#x27;t expect a problem will be solved if it&#x27;s not even acknoledged.<p>Also let me insist that these are heuristics I apply to what I use for my own consumption, usually to create private tools that will make my life easier, or just to learn something satisfying.<p>That said, I bet you know Haskell better than me. The fact you singled it out asking about it makes me suspicious it shows at least one of the red flags :-)<p>If that&#x27;s right, I don&#x27;t care how <i>good</i> it is.