The only issue with microfleece is the that they are not all created equal. The cheaper in price the less technology is involved in it, like say wind stopping properties. I own polypro base layers that do more at stopping the wind than big thick piled fleece jackets. Because of the weave and such.

Layers. Layers. Layers.

I am actually thinking of switching to light wool base layers or heavy silk now that the prices are dropping. Those are about the same weight as a polypro base layer like a long underwear.