I put my MM K brace on several months ago and noticed a little bit of a difference. I'm sure from what MM states about it, that it is doing more than the simple 2-bolt brace. I think the biggest difference I could tell was that the front suspension seemed to smoothen out more. Even with my stiffer springs and other front stuff, the brace did help comfort wise and (from what I can tell) sudden turns and higher speed turns are now even more precise up front.
MM includes this brace in many of their kits, so there is something to it. I felt a bigger difference with subs, but at that time I had no suspension mods.
For $100, I think the brace is worth it, especially if you're doing other suspension stuff. Making the K member stiffer is always a good thing.