I tested it out this weekend with a brutal 1600' of WI 4+ climbing and the jacket was highly breathable and shed all the water dripping down me easily. It accommodates a helmet well and the hood cinches down.
I am 6' 185lbs and a medium fits perfectly. There is not much room for layering, but this isn't a jacket you would wear in the cold unless you are being super active. I put on a down jacket when I wasn't moving. The Welder has a slim, athletic cut and its made for active use, unlike other soft shells that will only see urban use. If you plan on wearing this in the city, err on the larger size so you can fit clothes under it. The sleeves are long enough that they didn't ride down or expose my wrists while climbing.
The only complaint is that the zipper got stuck. Its a small-toothed zipper, so it seems like this could be an issue in the future.
Even with the zipper, I would still recommend the Welder to anyone looking for a no frills softshell that is made to get the job done without breaking the bank.