Huge, Variety of terrain, Old-world experience, Skiing and Apres-Ski were invented here
Not a lot of beginner slopes.
I spent Christmas week in St. Anton in 2005. Awesome mountain. Variety of terrain; everything from comprehensive ski school areas to hikeable bowls, peaks and chutes. Skiied from St. Anton to St. Christoph (and back) on one day; Skiied down to Zurs and Lech from the top of the Valluga on another. Breathtaking views, tasty on mountain restaurants (real restaurants, unlike the mush you get at U.S. resorts), charming town, and nonstop apres ski.
If you hate skiing nongroomed runs, St. Anton (and Europe in general) is not the place for you. Grooming is what people do before they go out to the club not what the ski resort does before they open.
One of my top 5 for sure!