It does -not- weigh like a MacBook Pro, it is only 3.3 pounds (much lighter than the Jony Ive 15).
I am drowning in Macs at the moment filling specialized niches where they work better than the MBA 15", but if a higher power stepped in and asked me to keep only one machine it's the one I would keep. It's the only machine that's just good enough along every important dimension, including portability.
The 15" MacBook Air weighs the same as the 14" MBP. Only 90 grams difference between them.