I ran the Glass City (Toledo) marathon this spring in Adidas Cubatos even though I was told by many people they are too light for marathons. They seemed ok, though it was hard to tell since extenuating circumstances (33 degree rain on hamstrings, 10 miles of hypothermia) caused a lot of leg damage regardless of the shoes.
I plan on using this model again in Chicago next week in a 2:29-2:31 attempt. I'm interested what shoes other fairly quick people are wearing. I'm a little on the larger side for the distance (5'10", lean 150 lbs) but with a pretty efficient form I think it is possible to get away with these lighter shoes.