in practice, overloading introduces overhead that might hamper performance.
You mean overloading in general, so using type classes? Is this comparable to the Java/C#/C++ overhead with virtual methods, so one extra level of indirection before the function gets called? Or is it much worse?
usually, don't worry about it. if a program really is slow, still don't worry about it, but find out where that program is slow. only if a program is slow in an area that uses overloading, see: http://www.haskell.org/haskellwiki/Performance/Overloading and even there, the advice is not to avoid overloading, but to make sure that you use specialised versions of overloaded code (by giving more specific type annotations or specialize pragmas, or by inlining overloaded code into usage contexts where its overloading can be resolved to specific types). claus