I think the pile pertex concept is great, and as long as the weather is cold enough, for me its the most comfortable system out there. It isn't waterproof, but I don't care, because worn next to the skin it's very comfortable and as stated, dries quickly. The only caveat that I've found really is that the system works whilst you are reasonably active, for long periods of static, a more conventional insulation system may work better, or alternatively use it as part of a layered system. The Montane version also has a hood, at no additional cost. It does, I admit, feel a bit strange at first wearing it next to the skin, as it was designed, but you soon get used to it.
I've often wished I could find a similar system for legwear that wasn't too hot, but the outer would need to be more durable than pertex for the terrain we encounter in our world, also not being waterproof could lead to wet boots. Maybe they could be paired up with some sealskin socks or something. Food for thought anyway.