Counter anecdote: I've been carrying around laptops since my 17", 13# Alienware "laptop". Ever since the release of the 13" MBP (the one with the CD drive), a decent backpack or messenger bag has effectively negated every thickness and weight gains from that point on.

Frankly, I'm more annoyed by the bulk and weight of the power adapter than I am about 1mm or 1# off the laptop.