You've hit all the benefits pretty well. Another big thing is frame quality. A good frame has to be stiff in all the right places and compliant in certain places as well. I found it much easier to climb and accelerate after I upgraded to a carbon frame from an aluminum one, though part of that might have simply been the placebo effect.

With wheels, unless you're doing time trials or something, aerodynamics don't really matter all that much (IMHO; some people disagree). What I look for when I buy wheels is low weight. The less rolling mass you have, the less effort it takes to go fast.

You do have a good point about prices. Most people feel that even $500 is way too much to spend on a bike. But like you said, it's definitely one of the healthier things to spend your money on. I'm glad you're not one of those people who thinks people are retarded for spending so much money on a bike.

Creeped through my pictures? :p. I just got a full carbon saddle and haven't had a chance to do any long rides on it, but I've heard that it's much more comfortable than a "conventional" saddle because it flexes more. I'm skeptical, but we'll see. I'll probably do a century soon after I finish with finals.

I do own a commuter as well. I got it for $150 4 years ago and it's still going strong :D.