Seems like we have a lot of windshirt choices these days, and I am glad people are calling out which ones breathe better at one end of the spectrum, or repel rain better at the other end of the scale.
Glad to hear the Houdini breathes well; I have one but haven't had cause to use it yet. The full length zipper and hood, coupled with light weight, make it may emergency "must carry" rain/wind/sleep jacket. My former Dragonfly was too hot, although it repelled rain really well and has found use as a sleeping jacket to keep my bag clean and my head a little warmer.
I will be trying my old Patagonia Helium (before they moved to the smoother finish recycled polester version) on my next trip to Sunrise High Sierra Camp, but since I walk "hot" it probably won't come out until camp (unless the skeetos come out); when I tried it a couple of years ago, it was fine as a windbreaker but unsuitable in any serious rain.
I also have an untried Wild Things Gear thin nylon windshirt, which packs small but which got overshadowed, before any real used, by the others. The all black one I have makes good urban wear, or airplane wear, though (I reserve the expensive Houdini for rain in order to preserve the effectiveness of the DWR).