Again with the “portable” comments? If you consider a laptop portable, then so is the PSP. Pocket-sized it may not be, but i'd expect it roughly the size of Sony's Nx-series of PDAs, which are a little longer than standard PDAs. The disc-based nature of the device shouldn't add much more size, shock sensitivity, or power consumption to the device as any recent Minidisc owner can attest. "Shock proof" is even noted in the specs.
The 7.1 sound is interesting. I remember Rick Powers saying how cool it would be to have Dolby's headphone technology incorporated into a handheld system. I had thought the same too, although power and CPU usage seemed like it would be too high. Looks like Sony's using their own surround sound tech in the PSP to emulate Dolby and DTS's technologies, although it's worthwhile to note that even Dolby's technology only employs five channels (six if you include the LFE channel mixed into the left and right speakers).
Remember that the device will be used to play movies as well, which would be the best use of 7.1 sound. I don't expect it to be used in a real time environment (ie games), at least not all eight channels. I also don't expect it to be true 7.1 sound, with a true LFE channel. In any case it looks like i may be able to finally put my earphones to good use on a portable game system.
Regarding heat, i think it'll ultimately depend on what's being used, although i wouldn't be surprised if it got hotter than the GBA based on the sheer amount of hardware. Battery life will also be dependant on what's being used, but i'm sure it'll be shorter than GBA's in actual use. But if Sony's shooting for an older market, and i've posted this before, what's the big deal? How many of us in our late teens to twenties have gobs of time on end to play games? How hard is it to drop a device in a cradle to recharge it? Have i've gotten too accustomed to my bi-daily cell phone and PDA (before it got destroyed) chargings, or for those of us in that age range is it just not that big a deal?
Now if we could just get some info on price and games.