I'm hoping that the more expensive helmet are better, otherwise I have just thown away a chunk of change. My current helmet is a low end Trek badged model that was fine when I was riding at an average speed of 18 mph. During the last year I have put in a bit of work and now I'm riding a quite a bit faster and hence putting out more watts. My old helmet was fine during the Florida winter, but now that the weather is hot and humid I am getting a river of sweat running down my face after twenty miles even though I am wearing a good sweat band. I splurged for a Giro Atmos from Nashbar because they had a deep discount on an '05 model in red and blue and I should be getting it tomorrow. My hope is that the better ventilation will help with this sweating problem and possibly have a performance increase by better cooling. The human head is really important part of the human cooling system. I have no idea how those pros can survive time trialing in their aero helmets that look like they offer no ventilation.