Definitely great for layering - this isn't a "warm" shirt on its own but it's comfy under a vest or jacket in cold temps, and I think it will be perfect for the spring/fall.
I love the longer length and the fit of the arms. I am 5'8" and 150 lb, size 6-8 in Oiselle usually, and the medium was perfect - slim cut, but not too restrictive.
The colors are lovely, and I get a lot of compliments on the cute birds when I wear it casually. It's great to layer under sweaters since the fabric is so breathable.
Very happy with this shirt!