To add to this, I was running a few tests today with a 5v pack "PowerPack" and the pineapple would crash if I messed with too many things in the Web UI, or after about 5 minutes. This was on a recently flashed pineapple with about 5 infusions installed. It would do this with and without a USB device connected (in my case, a Linksys WLAN card). Afterwards, I ran the same tests with the 12v Juice over an hour and have yet to crash. It may just be my 5v that causes problems, but I'd just stick with the 12v.
