I just spent a weekend in a Browning "Gator Fleece"- seems pretty good at
stopping wind. This garment does not have pit vents. However, it is a
breathable fabric. It was about 20F with steady wind of 20 mph with frequent
35mph gusts. Body stayed warm while hiking and was still ok when we stopped
for lunch behind some poor windblasted tree alone on the ridge. Damn near
frostbit my face though. The fabric seemed to not build up a lot of
moisture, even after climbing through about 1000 ft or so of elevation gain
& it isn't too heavy for a single layer, and it keeps the wind out. I
haven't tried it in rain conditions yet. Browning recommends a gore-tex (or
other "breathable" waterproof outer) shell only if its really raining. I
think it only comes in camo- but I'm not sure about that. I did get pretty
chilled there for a while and I was having rude thoughts about the shell
when I figured out I had a couple of chest high pockets open- mesh pockets,
zipped them shut and stayed a nice comfortable temp.

I tend to think if the temps were 30f or above- it might be too much if your
going to be hiking- standing in the Clearwater steelheading in February
though might be fine- we'll see.