I was in Whistler last year with family for a few days. I hired an Enduro and went out with a guide twice, and had an absolutely fantastic time.
The trails are stunning, nothing like what we have over here. I'd be back over tomorrow if I could! Also, in the town itself every 2nd shop is mtb, ski or otherwise sport related- I thought I was in heaven.
I think having to take your own bike may put a lot of people (with less impressive bikes like mine) off, so if you could arrange a deal with a local shop to hire a good one, perhaps with the option to buy, you'd be onto a winner.
Good luck with it anyway!