Living here in New Orleans where the temperature and humidity are regularly in the 90s F 7-8 months out of the year, I sprang for a Giro Pneumo purely for ventilation. I have not regretted a penny. The ventilation is wonderful, and the RocLoc 4 suspension system allows a wonderful fit. FWIW, a few months ago, Bicycling had a little blurb about one of the less expensive ($70-80 range) Giro models that they said was so close to the Pneumo as to make it a better bargain. I got my wife, who doesn't ride much, a Giro Stelvio on sale at a great price. It is a good looking helmet that I'm sure is as good as any. The fit system on it is very good, too. All helmets are pretty good.
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If it ain't broke, mess with it anyway!