I've got a business app in C#, with unit tests. Can I increase the reliability and cut down on my testing time and expense by using NModel or Spec Explorer? Alternately, if I were to rewrite it in F# (or even Haskell), what kinds (if any) of reliability increase might I see?

Code Contracts? ASML?

I realize this is subjective, and possibly argumentative, so please back up your answers with data, if possible. :) Or maybe an worked example, such as Eric Evans Cargo Shipping System?

If we consider Unit tests to be pecific and strong theorems, checked quasi-statically on particular “interesting instances” and Types to be general but weak theorems (usually checked statically), and contracts to be general and strong theorems, checked dynamically for particular instances that occur during regular program operation (from B. Pierce's Types Considered Harmful, where do these other tools fit?

We could pose the analogous question for Java, using Java PathFinder, Scala, etc.