You guys might be a bit biased.

I'm fairly overweight (215 lbs, at 5'8", age 35). I was very comfortable with 45 lbs in a really nice internal frame backpack for 46 miles of the art loeb trail last year.

I think the pack can make or break you.

I got a cheap pack recently (which boasted all the same features of the more expensive pack), and hiked out to the market in a snow storm, to get a 18 pack of Mich Ultra, and a bottle of wine for my wife.

The 2 miles back home felt like I had eighty tons on my back. I think the waist belt and suspension system of the cheap pack had alot to do with it.

Do I prefer 30-ish pounds... sure. But 45-ish isn't uncomfortable.