Be really interesting over the rest of the year to see how Apple fairs in the professional video arena, looks like their market share is set to drop considerably... I believe it was about 45-50% of the pro editing market...
I doubt it will be that big of a deal. There are always a minority who make a lot of noise about things and you would think that a product is doomed if you just focused on the negative comments. I'm sure Apple will address the shortcomings in the months ahead and people will then be singing their praises. They might lose a few users, but I don't think there will be that many people who will jump ship to the competition. Those that do were probably already thinking about switching.
I think that the average FCP user will adopt a "wait-and-see" attitude. With the negative press swirling, you can bet that Steve and CO will put put a priority on fixing the shortcomings. Not that they will make every pro happy, but I think most will come on board.