As an update I've been commuting on the wife's '06 Ducati Monster 620 for a couple of weeks now. An 11 mile commute in and out of DC so mostly heavy stop and go traffic with a quick blast on 395 up to 75-80mph for a couple of miles. Really not a fuel-efficent type of commute as half of it is with the motor not fully warmed and hardly any is just cruising at a constant speed.
The monster has gotten between 57 and 60mpg consistently (hand calculated) so far (temps between 60-95 deg F). I'm quite impressed. On the same route my DR250SE does no better. I don't ride in a really eco-friendly way - usually scoot up to the front at traffic lights then blast away from all the cages
The monster has a K&N filter, Termis and super-low gearing (don't remember how much lower but I think its something like 1F, +2R).