I agree with Feallen and AB, for the most part, but I don't think it's QUITE that bleak! Yes, it is busy during spring break, but most areas are, and the Summit County areas usually handle crowds pretty easily (with a few little bottlenecks and busy intersections, for sure). Keystone's extensive night skiing operation, unique in Colorado, provides more time options for avoiding the big crowds and eases the end of the day rush a little.
Keystone's night life is not its strong suit, but there is some. Still, a free Summit Stage bus takes you to Breckenridge, 15 miles away--the heart of Summit County's party and bar scene.
Early February or early April are better times than March if you want good snow and longer days, but don't like the crowds. But March is good skiing!