Interesting discussion. Since I switched to Nikon several years ago (during the 1DIII focus fiasco) I've been reading Thom Hogan (
www.bythom.com) who offers a lot of good thinking, mostly Nikon oriented.
He recently wrote about the idea that being "locked into" a particular system due to a collection of lenses and accessories is a bit misleading, particularly when you have used the system for a period of years or decades (high frequency switching is another matter). This was pretty much my experience when I made the switch, yes I took a hit on my Canon gear (and I still miss my 400/5.6 which still doesn't exist for Nikon) but I had used the system extensively for many years, so the annual cost of ownership was quite reasonable. Switching also gave me a chance to reconsider my choices of bodies and lenses based on 20+ years of experience and with a fairly good idea of what and how I would be shooting. So while switching is a bit daunting and you will likely end up with fewer bodies and lenses in the new system (at least to begin with) it is certainly feasible.
Another school of thought is to keep a foot in both camps and enjoy the best features of each system. I like this idea but it isn't practical for me because a lot of my shooting is on trips, and when traveling by air, motorcycle or bicycle it is hard enough to manage one system, two would be out of the question. But in a studio or even when traveling by car I could see it working quite well.
Over on
www.naturescapes.net E.J. Peiker is moving from a D3X + D700 (I think) to a D800 + D800E for a blend of landscape and wildlife (he is a duck expert, among other things). One of his ideas is to use the D800 in crop mode for wildlife – this uses the sweet spot of the lens and reduces the file size, although it doesn't increase the frame rate as far as I know.
To me this seems like an excellent plan, he gets the 36MP without anti-aliasing when he needs it (almost MF performance), he has two bodies with the same interface that share batteries, brackets accessories, etc., they are lighter and cheaper than the D3X or anything comparable, choice of CF or SD media (he likes SD because his laptop has a built-in reader so he doesn't need to bring one), a vast selection of Nikkor F-mount lenses going back to the 1950s (obviously with limitations on the older ones) plus many third party lenses. Throw in the excellent Nikon flash system and I think it is a winner.
And yes I am a bit of a fan boy, but I am sticking with my D300 + D3S for now.
Jeff