I bloody love my Decathlon x light jacket. I bought it with the intention of wearing it before/after rides – ie a cheap jacket that I didn’t care about it getting dirty. However, I love it so much and I spent most of last winter in it – wearing to work, out and about, walking, and i wore it pretty much all the time I wasn’t riding this summer in the alps.
I have a decent synthetic jacket (montane prism) which is probably better for being active but it’s nowhere near as snugly and warm on cold days.
The one thing I will say about the decathlon is that the cut is a bit odd for me. It’s perfectly comfortable/functional but it looks a bit weird, tight under ribs but kinda flared out in the hips. I’m probably going to buy a posh down jacket which looks better and might last longer, while keeping the decathlon one for its original intended purpose – knocking around in, getting muddy etc.