I have two different Terry boleros. I have the thicker original one that I wear pretty much all winter. It turns any short sleeve or sleeveless jersey into an all season one (because of it, I only own one ls jersey!). Like Emily said, it's a little thicker with a fleecy inside. It's also a little long in the sleeves for me, but I've got short arms.

I also have Terry's new lighter bolero. This one I bought this summer when I needed extra layers when biking in the NC mountains. My original bolero was a bit too warm and it didn't roll up as small as I would have liked when my storage/pocket options were minimal. This one is more like the long sleeve jersey material without the fleecy lining. It's definitely lighter and breathes a bit more...probably too light for real winter temps.

I love both and they both have gotten tons of use. I've been tempted by some of the others just because they are cute colors/prints, but these two (both black) have really suited my needs 100%.

Oh, and the zip one didn't appeal to me AT ALL. The part I like best about my boleros is that they are open on the chest. My chest rarely gets cold and once I'm warmed up from biking, I swear that's where most of my heat needs to vent. Even biking in the 30's, I can't wear anything thick on my neck/upper chest without broiling! I'm weird that way, though. I had the same problem with xc skiing and ice skating too.