First off, there's a thread for this topic here already:
http://forum.ppcgeeks.com/showthread...=38444&page=12 It's not really relevant to upgrading the Titan, more like replacing the Titan.
Anyway, as a note of interest, I believe we figured out in that thread that the only people getting a full trade-in offer are the ones whose Moguls are under warranty. Those of us whose Moguls are out of warranty don't seem to be getting any more than about $250 off, including the $75 sub-22-month instant discount.