Upload & Sell: On
Since I have owned the latest version of the Carry Speed strap (CSProII w/ C4 plate) for about 4 months now, I thought I would give my two cents to this thread. I have used the C3 plate before and have to say that I prefer the new C4 plate a TON more. It lacks the two risers (See Volks1470's pictures) that prevent it from being mounted flushly to the bottom of the camera in any orientation desired. Additionally, it has a rubbery grippy surface on it now that creates a more secure attachment to the camera/tripod mount (it wont twist on its own and it stays tight. In fact I have never had to re-tighten the screw on mine).
As far as the new ProII strap, it has the quick adjuster which lets you keep it tight and the camera held up high for when you are just walking around, and very quickly allows you to extend the strap out so you can get the camera up to your face. The only downside is that it drops on its own gradually with a heavier camera setup (Gripped 7D and 70-200 F/2.8) and if you lean forward your camera will come out in front of you potentially endangering it, or at least causing an inconvenience.
I have to admit that at first the size of the plate deterred me because I like to shoot in portrait orientation quite often but it does not really bother me, and I have tiny burger king hands.
Finally, having met Tim personally, and talking to him extensively at CP+ in Yokohama this year, he truly seems to value customer feedback, which is probably why the Carry Speed designs change a lot.