I'm with roadworthy. I for one would buy a 400CC if they made them. Especially with $5 gas on the horizon. I plan on riding a lot more to work this year.
I have a friend who commute on a KLR at 50MPG, and another the commutes on a Rebel 250, he pulls better the 60 MPG! I wouldn't mind doing that on a Triumph. At least then you'd look a lot cooler!