I'm often asked why bike weight is so important. "Rather than spend the extra money, couldn't I just skip breakfast for a week and lose a few pounds?" Well, for health reasons, I would always recommend losing excessive body weight, but it isn't really going to make you faster like a lighter bike would.
The best analogy I can think of is that bike weight is like carrying a suitcase. If you have a thirty pound suitcase to carry, and you lose five pounds of body weight, the suitcase doesn't get any lighter, or easier to carry through an airport. But if you remove five pounds from the suitcase, it's much easier to carry. Same thing on the bike, except it's weight you are pedaling up hills, and weight that takes more energy to move after each stop. Lighter bikes are more nimble, climb better, accelerate faster, and simply put, are just more fun to ride.
Even a pound or two, especially in critical areas such as the wheels, can make a huge difference in your performance and enjoyment, especially on longer rides. Because of breakthroughs in metallurgy and the use of new materials in both frame and componentry construction, bikes are getting lighter every year. Entry level bikes now out perform bikes that cost twice as much 10 years ago, and you can buy a mid level bike these days that in the George Bush Senior era would have been a show bike, unobtainable at any price.
Maybe it's time to retire that old iron horse. Come in and test ride a new miracle metal bike today.