Wow, they got rid of the chibi proportions to the characters. The areas shown so far look really good, and different enough from X/Y and OR/AS to pique my interest.
The starters though?
Grass - Rowlet is kind of dull looking, or maybe it's just my indifference towards owls in general peeking through.
Fire - Litten is, IMO, the best looking one of the bunch. Its design holds the most promise to become something awesome looking, or at the very least, it's unlikely to veer into something hideous.
Water - Popplio... Oh boy. Ever since I was a kid I would pick the water starter for my first run of a pokemon game. However, Oshawott burned me so hard I almost passed up Froakie in gen 6. I was never sold on Oshawott's design (again, a little seal with clown design elements) and his look got more and more awkward as it evolved. I'm not taking my chances with this one, as I've disliked every single aquatic mammal pokemon Gamefreak has created to date.
The legendaries look better than the previous gen's efforts, and probably the strongest box art designs since Giratina's Origin form. The sun one especially has managed to hook me, even though it looks like a Pyroar's mega form. I also like how it fits into its cover better than its counterpart.
This trailer has accomplished its job. It's piqued my interest, got me talking, and left me hungry for more.