We've had similar discussions over on the Leaf forums. If GM and Nissan would include an auto-sensing 120V / 240V EVSE that would really help a lot. Many people would not need to spend the money for a second EVSE. At least with the Volt I consider 240V charging to be a luxury, due to the nature of the vehicle being range-extended. However, with a Leaf it is a necessity for most people.
Ironically, since my wife bought the Volt 2 months ago, I've been downgraded to charging my Leaf on 120V so she can have the 240V charger. This is primarily because I drive 10 miles per day and she drives 40. And I'm using the Volt's L1 unit to charge my Leaf since it mounts nicely on the wall compared to the Panasonic unit provided by Nissan.
2011 Blue Nissan Leaf SL (No QC Port)
2012 White Chevy Volt