I use the GoLite Ether windshirt. It is cold and synthetic feeling next to my skin. I didn't like it at all, and it seemed to be pretty damp or sweaty feeling when climbing a grade. It seemed to block the wind, but conduct the cold from the air/wind -- even under a base layer.
Normally I use my old capilene (Patagonia) midweight (I don't know what it is called in their new 1 - 4 or 5 rating system)next to my skin for the upper (6 oz.), and my old expedition weight Pat. capilene long johns for lower base layers (8 oz.), if I wear any long johns -- depends on the weather. I don't even notice them.
I use a 1 oz. Mountain Hardwear balaclava and Micro dome (1 oz.) for head cover if it is windy under the hood on the GoLite Ether in pretty cold weather and I don't get cold, or too cold. I am looking at a heavier, lined balaclava, the OR Gorilla Windstopper (3.5 oz.) to add to my gear for heavier weather. I love the hood on the windshirt over that gear.
Because of the discussions here I ordered a Patagonia #2 merino wool synthetic blend pullover long sleeve for the upper. It is 3.5 oz., same as the GoLite Ether. I believe it is going to be very comforatble, avoiding using the windshirt next to the skin.
So torso inner layer is going to be 3.5 merino wool/synth. blend, windshirt is 3.5, then if I use the Drop Stoppers or a Poncho it is all together about 12 oz. for the uppers. When exercising in moderate weather I figure that will get me down to 10 F with precipitation/snow or cold rain. Under 10 F I am going to replace the Drop Stoppers with a heavier Gore-Tex Jacket or hooded jacket of some kind, presently use my old North Face ski jacket when worried about geting wet, but it weighs like 18 or more oz.
IMO my mid layer of Polartec, deep zippered, pullover pushes the temp. rating down to 0 F and the weight to 18 - 20 oz. using the Drop Stopper jacket. So far that system has worked down to 10 F frequently when hiking or exercising, like carrying or cutting wood in the wind. I believe it will work down to 0 F, the few times it has been zero it worked. When I use the gear in weather then I assume it will actually work for shorter periods down to below zero, but then it becomes a safety issue for me so I wouldn't push it until I get more experience.
That is my system so far, but I am learning so much here it is hard to say what it will be in a month.
The windshirt is always with me, but it is most useful to me when worn outside the base layer and the mid-layer, when I wear one -- which is often. I wear it that way because it does what it is supposed to do w/o being next to my skin - because it feels weird and gets cool, or once or twice cold.
What I really like about the windshirt is the hood when the wind picks up all of a sudden and I don't want to bother with a balaclava for 5 minutes until the wind dies down.
In any case, it appears to be a real personal preference matter, after reading lots of different comments and posts related to the topic here at BPL. (Just ordered Ryan Jordan's book of essays on mountain clothing and gear.)