Battery life has pros and cons. When on and operating, the device has a very low energy consumption. I haven't brought it to charge zero yet in my use pattern (it's only 2 weeks I've been playing with it) but it seems that the 10 hours use promise is true. On the other hand, when it's suspended to ram, it still consumes enough energy (it's clocked to 14 MHz according to its engineers) to suck the 4000 mAh battery in about 24 hours. So use it or turn it off! At least until they find a way to lower current consumed in sleep state. The bootstrap time isn't particularly long, indeed, apart for the first time.
One thing you should do when you get it is update to the latest version of the nand firmware. It's a breeze: you download it as a zip file, expand it to the root of a sd card, place it in the left slot, turn the pandora on with right shoulder button pressed, and when you get a boot menu, you choose to boot from the card - this flashes the firmware to the internal nand.
Then, you can transfer the firmware to the left sd card, if you like. I think it's better, to spare the nand use cycles and to have much more space for it. Instructions are on the wiki - it's easy even if slow, and I had no issues with that. Presently, my firmware is again on the nand, because it's the RC1 of the new version, and I'll move it on the sd card again when it's final.
Concerning clock speed, you have the option of choosing lower and upper limits of clock, upper limit of cpu voltage, and initial clock when booting. If boot crashes, the subsequent one gets reset to 600 MHz. You can also change max clock on the run through a menu command with a slider.