I'm very pleased with the gameplay and the amount of detail given to the world. I have no complaints to give there - Breath of the Wild will clearly be a fun game.
However, I am a little worried as to what kinds of character we'll actually see in the world. We've already received confirmation on no real companion character existing in the game, so it looks like all exploration will be done alone. It looks like you're introduced to one character at the beginning of the game, and you briefly encounter other characters inside some of the shrines around the landscape. But we haven't seen any towns or anything of the sort yet, so it's tough to know how limited we are as far as interactions with other characters.
As it stands, I know that some would prefer a more isolated game where you spend the vast majority of your time exploring on your own. But I did enjoy having companions around in the past games, and towns and the like have always made for a brief rest from the rest of the gameplay. The flexibility offered from combat and exploration, as well as what looks like the incorporation of more RPG elements looks good for the series. But from personal experience, having that sort of gameplay going continuously without any sort of break gets old eventually.
I hate to be a downer by bringing up concerns like that. I'm still incredibly hyped for the game - at the end of the day, while I enjoy the characters and stories of Zelda games, they've never been a priority for Nintendo, and there's no reason to let concerns over them overshadow everything else. But I did want to bring up that little issue I have with what we've seen.
8/10 for now. It's the best game I've seen this E3, but I've still got some worries about it.