My main problem with the Pi is that it is very finicky... plug a USB device in, and it dies/connection drops and all kinds of weird things happen. I have seen none so far on the Black.
In fact technically RPi model B's official spec is that it requires 700mA. You can often get away with less, but you'll definitely start to hit 500mA+ under stress and with peripherals, which is above what USB can officially supply.
Your best bet is to get a nice solid cellphone wall-wart type charger, preferably rated 2A and up. With enough juice powering the Pi, all the issues relating to USB disconnects, freezing, and ethernet dropping stop happening.
Gonna guess that the stability you're seeing with the beaglebone is just from its much lower power requirement.
pi@raspberrypi ~ $ uptime
10:58:03 up 17 days, 13:45, 1 user, load average: 0.00, 0.01, 0.05
pi@raspberrypi ~ $Many USB devices don't work with the Pi. It's pretty picky.
pi@mia ~ $ uptime
15:40:15 up 94 days, 23:03, 1 user, load average: 0.00, 0.01, 0.05