I'm a Nikon man, and Canon's specs always seemed lopsided to me, yet the gulf between the recently announced full frame Nikon cameras is... well a gulf. It desperately needs something in the middle.
As someone who rarely takes sports photos any longer, other than the inflated RRP, I'm thinking the 5D3 would be ideal for me. I'm not going to ditch my Nikon gear and move to Canon (especially as it'll all go full swing again in a couple of years, and every other release thereafter), but if Nikon would make the D300s replacement a full frame body which sat somewhere around a stripped down D4, while still at 14-24mp, I'd be snapping that out of their hands. The D800 would be fantastic for where I primarily use a camera - in the studio, but I'd worry that in anything other than optimum shooting conditions with optimum gear it's going to be a bit of a handful.
I never thought I'd say this with the megapixel race of the past decade, but with the D800, if nothing else you could afford to be a bit more lax with your framing rather than spending the extra time to recompose, only to lose that fantastic split-second a smile that'll never return. I'd find that a real bonus working in a school, doing portraits. I'm ashamed to say it, as it's pretty much the exact opposite stance to what I was brought up around, but other than ginormous prints, the pixels would have their uses.