My RaspberryPi 2 looks to have an intermittent fault on the USB bus - USB devices aren't always registered on boot or insertion, when registered they also randomly drop out and reappear. Same goes for the ethernet port (discovered when attempting to trace the problem. I generally use a wifi dongle).
Ordered it the day after it was announced. Noticed there was a problem a few days after receiving it when network shares kept disappearing. Have swapped the SD card, wi-fi dongle, power supply, checked routers, etc.. Contacted the supplier and am currently waiting for them to confirm I can return it for replacement.
This is my fourth Pi and the first I've experienced a problem with. Given the number sold, I guess it's only reasonable to expect a few duds that sneak through quality control.