I haven't had a prof fitting but I agree w the earlier response that talked about comfort of carbon over aluminum. Hills were easier, I hit two bumps and hardly noticed. I rode 1.5 hrs today and not one pain. I was def able to notice the differences between the bikes while riding today. The madone 5.2 shifted and breaked like butter. I want that bike. We didn't bother measuring after the ride. I will still have an ION when the more comfortable bike is what I need. Now to convince my hubby that I need a more expensive bike than him AND another bike when I just bought this one year ago