This is about as light a softshell as Patagonia makes. I think it is about as light as anybody makes in the current mold of textured softshells, as opposed to Houdini – class ultralight windshells.
To make sense of when it would be comfortable for me, I decided to put it on over a short-sleeve tech-T - long wind-resistant pants and synthetic briefs below, head covered by a ball cap and running gloves for my hands when I got cooler than desired - to take a walk with a local naturalist group. All walking is going at a pretty brisk pace, but there are lots of stops to scope out birds and other wildlife, and lots of meandering around things of interest. It was sunny out, no real wind to speak of, temperature between 46 and 49°F. I stayed on the cool-to-chilly side of comfortable. Which is to say that, if you had suddenly handed me, say, a Nano-Air or Adze Hybrid, I would have taken it. But I didn’t truly need either of those, and stayed engaged in where I was and what was going on rather than in being upset about chilly. Which I guess is what “chilly side of comfortable“ means. This might be slightly less warm then the old Simple Guide jacket, for anyone familiar with that. If I had been running, cycling (with hills), doing a serious hike (ditto), or Nordic skiing (same) in the conditions in which I did this walk, what I was wearing probably would’ve been more than adequate, in fact I might have worked up a little bit of a sweat which I most certainly did not under these circumstances.
All in all, I would recommend the Dirt Craft for conditions running from the mid 40s to about 60°F - the latter with no sun and spitting precip - for sustained aerobic activity. If you are just going for a walk, you will want something slightly warmer than this. But used as recommended, I think you will be happy because I know I would be.