I definitely agree with this, some form of ventilated jacket with an Under Armor shirt underneath works great. You'll still sweat, especially stopping at lights or in traffic, but once you get going, wind+sweat+UA shirt = nice cooling.

I will say that my perforated leather jacket vents just as well as my all mesh jacket while moving. At a stop the leather is a bit heavier and gets a little warmer (but its almost all white which I think helps some). Once I get going though, they both function the same which really surprised me.

 

I've gone as far as freezing some wet paper towels And shoving them in the pocket of my jacket where the back protector is. Feels great on the back but melts fairly quick. I've commuted in 100+ a couple times and it sucks but I'd rather sweat then bleed.

 

I just bought the Fieldsheer Ice Vest. I'll let you know how it goes when I try it out.