Yup. Nice area, right splat in the middle of the Monterossa complex (note that there is no longer a cable car up to Punto Indran, which kind of sucks). There are three villages at Gressoney, with the lowest one the most charming/least convenient, the highest one the most sterile/best access. The one in the middle is so-so all around. There's an awful lot of skiing to be done in this complex, even without Punto Indran.
Easily the most convenient resort in the area if you don't have a car is Pila. You could also ski Cervinia/Zermatt relatively easily with Ivrea as your base. Probably La Thuile would be doable too.
Here's the timetable from Ivrea to Aosta. A gondola runs right from the town of Aosta to the ski area, Pila, above. Very cool. I'm guessing that would be your only pure train option (hell, it's only about an hour's ride!), but there may be busses from Ivrea to other resorts.
http://orario.trenitalia.com/b2c/Tim...=tcom&x=29&y=7