The Canon/Nikon rivalry is rather amusing - and I think it will hot up with the arrival of Nikon's latest offerings that threaten to give Canon's offerings a run for their money. The AF issue with the 1D MkIII cannot help Canon's reputation, no matter how much effort they put into solving the problem. There have been other recalls too, remember the 24-105 f/4LIS recall and one of their later lenses too.
If an unreliable camera means a pro tog misses a shot of a lifetime, he/she will be tempted to swap brands. I've heard rumours here that some pros are doing just that.
Competition is a good thing, it keeps both companies on their toes and keeps prices keen. Complacency kills innovation.