Shortly my town will be adopting the 2008, and this will bring about new awareness of the requirements of feeder sizing, due to the fact that the NEC has made it clear that 310.15 B. 6 applies to a single feeder carrying all the load of a dwelling. Couple that with the new temperature rating for ser cable to the 60 deg column in 310.16 and the feeder sizes will increase by an avarage of two sizes on most new dwellings. Stictly my own opinion, but with the proper sized overcurrent protective device ahead of the "sub' feeder, the old sizing standard used for ser cables was already more than adaquate for the real life loads encountered. These new rules are huge overkill, but still it is in the code, so therefore it is just how it is, like it or not.