Same here. Took the watch on this morning at 7 am . Used it not a lot. Actually I used it as much as I would assume someone with such a watch will use it. Of course first day and I may have played a little more with it. Long story short at 8 pm the watch went into power savings mode...
Hey Apple thats 13 hours and not 18 !!! Where did my missing 5 hours go?
I may send the watch back...
Yeah def do that on a one day test and without waiting for the imminent software update, it's what anyone sane would do.....