Pom,
You actually turned that argument around on me. I'm not a Nikon fanatic; I think Canons are great cameras. I've suggested on this forum that a guy who was thinking of switching to Nikon, from Canon, think it over, since he was already invested in the Canon system.
What I was trying to get at was that people seem attracted to full-frame, but they don't seem to know exactly why, other than a general sense that it's better. What I want to know is, how better? And is full-frame "betterness" worth dumping an entire system, to buy new in another system? My argument is that maybe it is -- but not specifically for the full-frame effect. If you *really* need shallow depth of field at *specific* focal lengths, all right, maybe full-frame is better for you. But that's a pretty small group of people; and for most folks, not enough reason to dump one system for another...
I'm arguing that unless you have way more money than you need, you should take a very hard look at reasons for changing systems, because it's so costly. And there are implications to changing -- if you're that much in search of a certain kind of perfection, that means that you'll probably also want the most costly lenses, which is even more money with a switch.
Most people who I've seen on this forum and others, who are talking about switching, seem to have a vague yearning to swim upstream with the other salmon, but the yearning most often doesn't seem to have much with what they're shooting...
JC