Just to clear up any confusion on "summer", "winter" and "all-season" tyres. They are 3 distinct and different types of tyre, each having their own strengths and weaknesses.
Summer tyres are just that. Tyres for summer. Tyres that work best in temps above 7 degrees and generally have the hardest rubber which may wear at a decent rate too. They are NOT all-season tyres. I say this because a lot of people seem to think that their Goodyear F1s, Tuerenza, Continental Sport Contact, etc. are tyres for all-year round. They're not. They're summer tyres.
Winter tyres are a softer compound which grips better at lower temperatures and have thousands of sipes cut into the tyre. These are the minute grooves which collect snow in them and then use that collected snow to grip the snow on the road and give you better traction. Much like when you're building a snowman - you start of rolling a small ball and as you roll it through the snow it picks up more snow and gets bigger. Snow grips snow.
Modern winter tyres generally will wear a bit quicker than summer tyres - but not always. The science has come a long way from the days of very soft rubber and many people use these all year round with no trouble although stopping distances in the dry can be a bit longer than a summer tyres in tip-top condition.
My personal fave is the all-season tyre. Much more convenient cos you don't even have to think about changing wheels/tyres as the winter months close in and not the "compromise" that most people may think. They are very good in all conditions as they have both characteristics of summer and winter tyres. For example, the Vredestein Quatrac3s have a harder outside shoulder, much like a sporty summer tyre. This gives very good traction when pushing on a bit through the bends and makes the tyre a bit more rigid than an out-and-out winter tyre.
The centre and inner surface of the tyre have more grooves - and, importantly for excellent grip in snow/slush/ice, have thousands of sipes. There rate of wear is comprable to many summer tyres but they perform much better at colder temps too. I haven't noticed mine to be particularly noisy either. Not the quietest I've ever used but certainly not a problem.
I have summer tyres on my 17s and all-season on my 16s which may seem a bit strange but that's beacuse many moons away I acquired the 16s for free with a couple of all seasons on and I've just gone from there.
But if I wasn't lucky enough to have a spare set of wheels I'd definitely have all-seasons on my 17s. It's a no-brainer for me now having experienced how much hassle and stress they take away when things get snowy and icy.
Yes, you can manage on summer tyres all year round but it really does depend on the georgraphy of where you live. Here in the Peak District there are many roads I have to travel on that I simply couldn't in winter with summer tyres on. I know, because I've tried - and yes, I DO know how to drive in snow! Sometimes I would struggle and just about make it. Other times I've had to turn back. With the all-seasons it has been a breeze. Night and day difference. Honest.