This has been around for about a week, but still amazes me:
Also important will be the Galaxy Gear's battery life. It does use the Bluetooth 4.0 Low Energy standard to communicate, but at 315mAh its battery is decidedly small. Samsung promises "about a day" of endurance from the Gear, but by the end of our briefing with the company, the cameras on most of its demo units were refusing to turn on due to the watches running low on power.
I gave up wearing my 2011 iPod Nano as a watch not because it lacked features, but because I needed to charge it every day. The next thing I wear on my wrist needs to have a considerably longer battery life, especially at $300.