Thomas B.wrote a review of Mountain Hardwear Effusion Power 1/2-Zip Top - Men's on December 7, 2012
Familiarity: I've used it several times
This has become my go-to running jacket in 35-45 degree temps. A little colder if it's not windy and a little warmer if it's very windy. It breathes well and is vented in all of the right places. I usually wear it with a shortsleeve baselayer underneath but I have also worn it with a light longsleeve baselayer.
The jacket is well constructed, light (not overbuilt), has everything I was looking for and is true to size. The only reason I did not give it five stars is because it is a little short in the torso, which seems to be a recurring problem for MHW. Unlike some of their shirts and jackets, however, it is long enough that I did not have to return it.