Another Hands-on video and a theory
Here's another handson video which shows some web browsing.
I have a theory about the 9900 1230mAh battery life: Since OS7 leverages from the built-in GPU for graphics and not/less from the CPU, the battery should have a similar uptime as a 9700/9780 (as stated in the video). GPU's in general are far more efficient in rendering graphics compared to CPU's, so it takes less time/power to render graphics which means longer battery life. So I think we don't have to worry about the less powerfull battery of the 9900. I also think that is the reason that OS7 is not compatible with the current models. Does that make sense?