Canon service is pretty bad in Canada, according to former Canon shooters. They love NPS and how they deal with professionals. I'd also suggest that Canon's advantage in AF has long since evaporated and they're equal now.
I'm a lifelong Nikon user so take it for fwiw. Canon has rarely, imo, innovated with lenses and they only brought out a 200-400 after they realized how useful that range was. That this lens was also one of the most popular loaner lenses at the Beijing Olympics had some influence I'm guessing.
Canon has always lead in fast lenses (1.2) but they focus brutally slow and your margin of focus error was basically zilch. So 1.4 is fine enough for those who love to throw backgrounds oof.
When the 850 comes out, I'll get one for evaluation and probably end up with a couple.