Alcantara is a chemical compostion non-woven material composed of 68% polyester and 32% polyurethane. It was developed in the 70's by a Japanese scientist and involves some complex 'spinning' to create. Its sometimes referred to as 'microsuede', but its not a leather product.
There are a lot of imitators out there. The real deal comes from Alcantara SpA which is a joint venture of an Italian chemical company and Toray, the Japanese company that invented the material. Imitation materials will fray when cut with scissors, real Alcantara will not.
How will it wear? Well, like most things if you keep it clean it wears quite well. I'm in the leather/fabric business and the # 1 killer of all leathers/fabrics is failure to keep them properly cleaned. Steering wheels in particular are magnets for hand oils and grime, which will break down any material - even leather. Just give them a wipe down when you wash your car. You don't need anything fancy, plain water will do, or a little mild soap (like a swipe on a rag with a Ivory bar bath soap) will do the trick. Not too much soap, not too much water.
I have in in my Boxster and its terrific.
-Duane