I'm not aware of a language that allows operator overloading for matrix operations, but denies you access to c.Mul(a,b) or the equivalent when you need it. I find operator overloading pretty crucial for prototyping this sort of algorithm even if I'm later going to refactor it for performance.

edit: rereading the earlier comments, this may be orthogonal to the GP's claim that operator overloading is crucial for generics. Ooops. :)