Unityped vs multityped

Performance Warning: Matrix values are arrays, as exported by math/array. The same performance warning applies: operations are currently 25-50 times slower in untyped Racket than in Typed Racket, due to the overhead of checking higher-order contracts. We are working on it.
http://docs.racket-lang.org/math/matrices.html

Still not convinced that unityped languages suck ass?

>>31
No, it's not ``kindergarten level'' at all. It's very useful to separate expressions from values. For example this sentence would not be very informative if we didn't: `An expression evaluates to a value''.

Expressions can be values, or more accurately expressions can be represented as values, or even define what a value is (e.g. self evaluating expressions). But in general expressions are not values, they are evaluated to values.

Why is this controversial?