Sid Nitzerglobinwrote a review of Arc'teryx Accelero Hat on May 7, 2012
Has worked very well for high output hiking and trail running and doesn't look too dorky for casual wear. No itchiness after a full day of wearing. Breathes much better than I was expecting after seeing the thickness on the top panels of the hat. It still traps some heat (getting the black one probably didn't help this a lot either) but much better venting than anything else I had. Seems to dry relatively quickly but can stay damp for ~ 1/2 hour - 45 mins. if you work up a good sweat in it. Doesn't seem to show sweat so far like other hats I've used for active endeavors would.
Stays put very well w/o feeling like you've got a vice on your head, thanks in large part to the stretchiness of the fabric and the elasticized adjustable strap. It is a form fitting and low rise cap, but covers down to about a 1/16" or so above my ears on my ~ 7 3/8 size head. Fits very well w/ any of my sunglasses/glasses on. The bill came w/ a nice shape and seems pretty beefy. It provides good coverage w/o being obnoxiously long/large.
Only complaints I have is that the sweatband could be a bit more absorbent (probably perfectly fine for lighter sweaters or those in more arid climates though) and the price could be a bit lower.