* John Lato
In all seriousness, I'm not that fond of the proposal myself. I just wanted to argue the other side because nobody else was. But so far, I've seen two main arguments against the proposal:
1. IsString is for things that are notionally some sort of string. 2. It makes the types more confusing.
The second seems like a weak argument to me. First off, the proposal seems very similar to the recent generalization of Prelude.map, which had a great deal of support.
The difference is that fromString is called implicitly. A similar precedent is numeric literals. When I type 1, a method is called, but most of the time I don't need to think about it because those methods agree with my intuitive semantics of numbers. It's easy to define a more or less proper instance instance (Applicative t, Num n) => Num (t n) which would allow to overload numbers even harder, but then I'd need to stop and think every time I see a number. Roman