Battery life is my immediate concern as well. Between the big 'gorgeous' display (it's only simulated, so hard to call) and the high frame rate interaction I wonder if this will end up being another Galaxy Gear that may only last 12 hours.
eInk has serious benefits, especially when it comes to battery life. I love my Kindle. I can see how something like the Pebble would be a nice watch and eInk's battery drain is probably a big part of what makes it work so well.
But if you want it to feel interactive with a nice touch screen for swipes, eInk isn't going to do it. Take that video but change all the animations to 5 fps... would it be an amazing watch or just feel like a product that was reaching too far?
Similarly, color is a nice add but it could go wrong. The only pictures of color eInk I've seen look much worse than cheap newsprint. At that point the color isn't adding much, it's just detracting.
Samsung supposedly has much better battery life on the Gear 2. Keeping the display off most of the time would definitely help too. I want to see a review of this. If it's half as cool as it looks in their promo I'll be quite impressed.