In any cooler/windy weather, say below 70F, or above tree line in even a little warmer weather, my wife and I use the lightest weight Ibex merino wool l/s tops with deep zips. They've lasted quite a long time with good care. Also wear their briefs in cooler weather. Would never use anything but merino in cooler conditions.
Also like how the wool helps regulate your body temp - so for example, if you take off your outer layer, you won't get that immediate chilling effect you get with synthetics.
The only issue we have with the wool base layers is that in hot weather, especially hot and humid, smooth synthetic feels better and cooler against the skin, and in that case we'll wear either a thin synthetic l/s t about the weight of capilene 1 or 2, or in very hot sunny weather, will wear Ex Officio Air Strip shirts (and my wife's Mountain Hardwear equivalent) as they offer great sun protection, lift the material off you and have vents for breezes.
Unfortunately no synthetic with odor treatment is going to work as well as a natural fiber with wool with built-in anti-bacterial properties. Eventually the treatments will wash out of the synthetics. I also find x-static fairly ineffective (and had this discussion with a friend of mine who sat on the board of the company that produces it, pointing out merino wool as major competition).
Keep in mind that all the lightweight wool blends are supposed to have some polyester woven in for strength.
Perhaps a thin wool/poly blend closer to 50/50 would work best all around, if anyone makes one. Anyone know of one?
An interesting garment for warm weather would be a synthetic garment with wool patches in the funky regions, say a synthetic top with wool armpit patches, or synthetic briefs with a wool area in the middle in the groin and back.
Ibex? Smartwool? Icebreaker? Anyone listening?