Of the 32 resorts I've skied, this is in my top 3. Whistler/Blackcomb is wonderful, especially mid-week or on blue-bird days. A week's vacation will still yield ample room for discovery - both on the slopes and in the Village.
Despite WB's incredible depth and variety, the past few years have seen a severe degradation in the overall ski experience. Some weekends (esp. in late Feb/March) can see 45-minute waits on lifts at the Symphony/Harmony chairs. This woeful situation became so disappointing, I abandoned Whistler for Revelstoke - when I pay top dollar for lift tix, I expect to ski, not sit in lines for a big part of my day. Bring a fat wallet when visiting here.
Yet for apres-ski, variety and big-mountain experience, Whistler has only one serious rival in North America: Mammoth. Pick your moments: either in January, mid-week or on tamer parts of the resort.