I strongly disagree. If you're expecting the first value of a list, what use is nil?

If you have a list of Ints, then what can you do with nil returned? It's not an Int.

Nils have a habit of propagating through the whole type system, and you then need to have rules about how they apply to every function. (What is 1+nil? What is nil:[1,2,3]?).

Eventually every single function will either have odd behaviour when confronted with a nil, or will be a source of exceptions (which are generally undesirable in a pure functional setting).

Haskell encourages you to write patterns that check for these edge cases, and handle them explicitly:

foo [] = ...

foo (x:xs) = ...