Inquiring minds would like to know. 
Hard to describe - I'll try to articulate it, but doubt I will do it justice. Even though carapils=carafoam=dextrine malt, carafoam in particular seems to contribute a light sweetness and toastiness that complements well with the candy and hay-like character of the Best pils malt (Best, and only Best). It also seems to deepen the gold color versus the more straw like color when I made it with just pils and munich. It also seems smoother, but that might be psychological. Of course, I didn't do a side-by-side but I really didn't need to - once I made that change, it sort of 'clicked'.
Seriously, one of my closest brewing friends is a relocated Clevelander and he occasionally brings back some GLBC beers when he travels back home - we've had them together, and can't decide which is which.
Would decoction replace some of the dextrine malt?
I don't think so - certainly it would replace the melanoiden malt, but I don't think the carafoam - one, because at 8-9% you can definitely get some flavor contribution from it, and two, because my pro buddy uses carafoam frequently and he brews on a triple decoction 15bbl system, so I'm assuming if decoction replaced, why would he use it?
Can't wait - after my vienna this weekend, the next brew in line is the dort - I usually brew it at least 2, if not 3 times a year. The last keg blew back in October, so I'm jonesing.