The n8x0 also steped it's processor, and the n900's processor goes up to 600 as opposed to the 400 of the n8x0.
Unless this new cpu is much more power efficient (so much more power efficient as to account for the 3g radio consumption) I find it hard to belive it will last through the day with moderate use.
Let's face it, it's not a device to say you will use it lightly. You'll carry the expensive brick the n900 is because you use it's many functions.
Actually it's the only turnoff I see for now. Everything else is a hacker's dream. Fast, lot's of hardware features, decent camera, enough storage and more open than android.

P.S. the comparation with the iphone is wrong imho because the Iphone doesn't have to push 800x480 pixels around and because it's not multitasking. n900 will most probably used with many apps open through the day.

Class, repeat after me, pushing notifications over the air is not multitasking