I personally find that the subtle bugs it creates aren't worth the convenience, especially for string->number.
However, the "proper" answer depends on your audience:
- If you target people who will write complex code and maintain it durably, I think you don't want unnecessary magic that helps them lose track of their types.
- If you want to let power-users script an application of yours, and you don't expect them to be more skilled than an average Excel macro tweaker, then trying to circumvent their poor understanding of types might be a good idea.
