Ian gave his thoughts on the Catlike helmets, and I thought I would add my two cents.
I have historically had a problem with finding a helmet that would fit me well. Most are too narrow, or too long, or my head is too big for a medium but too small for a large. I find myself filling spaces with pads, which obviously is not ideal. My favorite helmet, acquired in a bike shop in France 7 years ago, is not sold in the United States. Always in search of a better fitting helmet, I tried the Catlike Whisper Plus. Unlike Ian, I took to the helmet as soon as I put in on in the shop. Next to my favorite, but now too old, MET helmet, the Catlike gave me the best fit of any helmet I have tried. I particularly like the way that the retainer system adjusts down the back of the head, allowing the retainer to be placed low on the rear of the skull. It holds the helmet firmly, but comfortably, on my head.
Unlike most helmets I have owned, I can almost feel what little hair I have blowing inside the helmet, and I definitely feel the air blowing across my bald spot. Some may find the styling of this helmet a bit too different from most other helmets on the market. To me, all of the vents, facing forward, and the large exhaust vents in the rear, create quite a draft inside the helmet. It certainly feels to me as though this will be the coolest (temperature-wise!) helmet I have owned.
All in all, I highly recommend this helmet. It couples a comfortable, versatile fit, with excellent air flow and cooling.