I bivied up on the beacons the other night to get some sunrise pics... it was COLD! Very alpine feeling; dry cold with the wind.
My kit doesn't actually change very much summer to non-snowy winter. Going lightweight I like my softie elite 3 SB and silk liner, full length multimat foam pad (one addition I take for winter) and 3/4 length thermarest. Actually I've got a link for the one I use somewhere...
http://www.rvops.co.uk/sleeping-cooking-76/sleeping-systems-28/multimat-length-1538.html no connection with them etc, but that thermarest is brilliant. makes such a difference and it's nice and light. Nanok -10 is what i've been using more for bushcraft where I tend to do less moving and carrying - the extra room in it is nice.
With clothing I'm not actually such a layering fan. I tend to be quite active outdoors and I don't like stopping once I'm moving. Clothing of choice in winter is a paramo adventure smock, and if it's cold a thin synthetic base layer underneath. Merino wool has been recommended to me a few times, but I've not yet tried it. The great thing about the smock is the amount of ventilation you can open up while walking / climbing so you don't start sweating and creating problems. I also carry a bivvy jacket for long stops or severe cold. Montane and buffalo are the other two popular clothing systems, though I don't have much experience with either. The military guys seem to love them though so I guess it's passed that test!
Decent pair of boots, big enough so you can move your toes and wear a couple pairs of socks if necessary. Goretex socks as the outer pair are great for where it's wet or boggy. Erm what else. Hat and golves obviously. If it's snowy the gloves'll inevitably get wet, so two pairs of thinner fleece type ones (one drying in my jacket while wearing the other) as well as a thicker more waterproof pair. Many wear mittens - old army ski mitts for example which are great and you can do a suprising amount wearing them when you're used to them. If it's really cold a balaclava really makes a big difference too, especially with the wind.
I think that's pretty much it for this kind of weather. Where there's snow or the threat of snow things change a lot, and where you are and what you're doing also makes a big difference
right, enough daydreaming about being outdoors in the hills, back to work for me!