In reply to Aiezsedai:
What's your budget? Sleeping bag prices are determined by two things: warmth ratings and weight/bulk. Good quality down bags will be roughly twice the cost of synthetics for a given temperature, but will average half the weight and bulk.
Example: Mammut Nordic 3 season, synthetic, comfort temperature -3C, 1250g, retails at my store (yes I'm a gear nerd, working in outdoor retail last 4 years) for €100. Good if you're on a budget but a lot of extra weight to carry up MB. Rab Neutrino 400, 800+ fill down, comfort 0C, 830g, €300. Much lighter and half the pack size, you get the idea.
I've been using Rab down bags for the last few seasons in the Alps and they are definitely the shit when it comes to down, but you need lots of $$$ (or a trade discount :P )
There's loads of advice on sleeping bags on the web without having to deal with annoying tangental forum discussion, I suggest you do your own research.
Another note, down does not deal well with moisture. If it gets wet, it becomes heavy and loses all insulation value. A big pro for synthetics if you don't mind the extra weight. A down bag needs to be paired with a good bivy sack. Basically if you have the money go for a good down bag and bivi combo, otherwise get synthetics and deal with the weight.
Both options however are a lot more expensive than a few nights in a hut.
If you're feeling particularly manly then I'd recommend getting two partners, splitting the weight of a tent/stove and climbing from the valley :P