Was just on Whistler Air this past weekend. We flew both ways and loved it (well, I did at least!). In my opinion it beats driving or taking the bus. The train sounds pretty good, but the timing didn't work for us. On the way up we flew a more direct route over the mountains and had amazing views as the weather was perfect. On the way back we followed the highway and didn't get very high as it was overcast. Still had some nice views though. There were a few more bumps due to the winds blowing up the valleys. The pilots let one person sit in the co-pilot's seat up front too so make sure to ask them if you are interested.
If you are planning the flight for a couple months from now, I would recommend leaving yourself enough time to take the bus, or other alternative, just in case. Fall is starting soon, and the weather will be getting more unpredictable.