I'm not a weight weenie.  First of all, I'm overweight myself.  Not grotesquely obese (I think), but like a lot of Americans, I could certainly afford to drop twenty pounds or more.  I ride a couple of mid-80s chromoly-framed bikes, which are light enough for me.  Not carbon fiber, but not a 1974 Varsity either (not that those weren't great bikes).

I see a lot of people out there claiming that it's not the weight of the bike that matters, but the combined weight of the bike and the engine, i.e. the rider.  The thinking goes, what difference does 10 pounds of weight on a bike make when bike and rider are 15 to 20+ times more than that?    

I disagree.  To me, my carcass is used to hauling its own weight around.  I think with most people, big or small, heavy or thin, their bodies and minds are more or less acclimated to whatever they may weigh (within reason).  So, I would remove that from the equation when dealing with the subjective impression of whether a bicycle is relatively heavy or light.  That 10 pounds that my Trek Multitrack is lighter than a Varsity is the difference between 28 and 38 pounds, say, or over 25%.  That's a very considerable difference, and I would definitely feel it, especially when accelerating or going up hills.  I know for a fact that ten pounds makes a difference carrying a bike up a few flights of stairs.  I mean, people who lug laptops around all day appreciate a difference of a pound or two.   If I carried ten pounds of potatoes around in my knapsack, I'd certainly know it.  So, I think that cyclists subjectively perceive bike weight primarily based on the weight of the bike, not on the combined weight of themselves and the bike.  

Sometimes I go for a ride in the park and leave my u-lock and front-wheel cable lock behind.  When I do that, I feel like a bird out there.  Even if some of it is psychological, I can definitely feel a physical difference.  I think that when you start talking about even five pounds of bike weight, most people would start noticing a difference.  Not five grams, probably not five ounces, but five pounds would be perceptible to even an average 250-pound rider, all other things being equal.  I'd be interested in hearing what the threshold of perception is for other Chainlinkers.  Probably a lot less than five pounds.

Or am I just delusional?