> or people that travel a lot, that 300 grams (.6 pounds) - is a deal breaker

I travel for business quite a bit (20-50,000 airmiles/year) and I traded in a 13" MBA for a 15" rMBP upon its release.

For me, it was an easy deal to exchange the laptop weight differential through unnecessary clothes or travel accessories for this gorgeous display and added (dev) computing power.