More clarity - as I said I'm not obsessive, and I don't feel I need more pixels, but that I would use more pixels. If more pixels were to come along, I'd enjoy the upgrade. I don't go out of ISO100 much, I'll usually flash first and get more control. More frames per second? I barely use one enough. But more pixels means more crop flexibility, more beautiful detail, better landscapes, more to experiment with ... Canon's upgrade path is for the sports crowd (frames, ISO and speed) which isn't something that matters much to me.
I remember watching the whole drama the first time digital broke 1 megapixel. I didn't buy though. I waited until the FIRST rebel, which I bought along with some nice glass at a crazy rebate they had back then (I got a fishy, 24-70 and 50 1.4). Then my next camera was the 5DMKII because I felt that finally the price of full frame came down to the point where mere mortals could afford it.
Now I'm shooting like crazy. Back in the film days I had an AE-1, and the cost of development kept me from shooting very much. Man I hated that ... and the long turn around. But now I have more money, and the technology is getting seriously wonderful, so I am putting more into getting the glass, pixels, and extras.
And because of this I'm taking tens of tens of thousands of shots - most of them bad - but you know this body is getting some serious work. Will it be getting pretty worn out in a few years? If so, I'd rather upgrade rather than send it in to get a new shutter, etc. So I don't lament the upgrade cycle on digital - the day to day cost is so much lower than film, who cares?
Oh, and I should add one more thing, one thing I hate about the 5DMKII is the crummy focusing system. I have a lot of shots that could have been great, if it wasn't focused on the wrong thing. I'm working on improving my technique to get better at this, but I would love a better camera. Sure, the III has the system I want, but it's not enough, for the price, to entice me.