I bought this as a ski layer, and to wear around town.
I was looking for something similar to a Patagonia R1, but that could also be worn around town. While the R1 is probably a bit warmer than the Nucleus, it is purely a technical piece, and you look pretty silly wearing it out as your outer layer if you go to a restaurant or run errands after skiing. The Nucleus grid-fleece on the inside, but is nice and smooth on the outside, making it nice enough to wear to work or restaurants.
With grid fleece, the benefit is breathability, but the downside is that it's not as warm as non-grid fleece, and while it's marketed as being a 'midweight' fleece, it is pretty light, and seems a bit thinner than the R1.
My main gripe is that the hood is quite large, to the point where I found it to be a nuisance when wearing it as a layer when skiing. I ended up returning it and getting the non-hooded version. I also tried the pullover version, which I found to have a bit of a tighter fit, and the grid material made it hard to get on/off, as it stuck to my base layer. I don't have that issue with the full-zip version.
Overall, after trying out several alternatives to the Patagonia R1, I landed on this and think it might be the best comparable piece out there. It's comfortable, looks good, the arms have pretty good amount of stretch, and its is pretty warm.