In reply to barbadose:
Attempting alpine routes at that time of year you'll find that it will of course be colder, and there's very likely to be significant fresh snow, so very great care needs to be taken if you're crossing a 'wet' glacier as the crevasses are very likely to be covered over, and as there'll be much fewer people around it's likely that the usual pathways across that terrain will not be visible. Many of the huts will be closed, though their winter rooms will remain open (and a stay in a winter room feels like much more of an adventure). So you'll really need to bring all your food + jetboil, etc., with you to cook with. Also, many of the lifts/cable cars will also have closed so the walk-in & walk-out will be significantly harder.
I hope that's of some help.