What other upgrades were you looking for when you went away from the 5D II and were considering a 5D III?
Build/weather sealing, resolution, DR, etc.
The 5D3 is pretty much the same as the 5D2 in those regards with a bit more power in the in-camera noise reduction.
The AF improvemens are worth the camera alone, of course, and I really considered it carefully but, in the end, I decided that I could afford the best and, since you only live once, I didn't want to compromise at this point.
I'm keeping the 5D2 (my wife claimed it) so it's likely that we'll upgrade it for her eventually.
For me, the AF improvements (drastic), plus being able to do AUTO ISO in manual mode at all possible ISO values, HDR, and Multi-Exposure, I'm not sure what else there would be as an "upgrade" without completely crossing into a different camera line. In fact, I don't know how they could have possibly upgraded the 5D Mark II any more than they did. I wish it had the color rendition of the 1Ds III at low ISO value. Maybe I'm just wishing there were a 1Ds Mark IV
For me, it would have been pro-level (1D) weather sealing and higher resolution. AF point metering would also have been a nice to have. Auto-ISO is nice, as are the additional multi-exposure modes, better video, etc. but the 1Dx has 'em all and more.
Yeah, I'm basically looking for a 1D lite, but for $3,500 I think that's within reason.
When the 5D2 came out it was a revolutionary jump in DSLRs with the resultion, video and so on.
The 5D3 feels like what the 5D2 should have/could have been if Canon hadn't gimped the AF on it...