As an adventure, it has some things to like and some things to not like and homebrew fixes for. As the foundation of a new edition? Its horrible because it makes the game feel like all combat and the presentation of side quests as NPCs standing around with question marks above their head gives all the wrong feel.
I'm not sure that's
entirely fair though. Bear in mind that this isn't really an adventure intended for us, it's an adventure intended for new DMs - it's intended to get someone new to the game up and DMing as quickly as possible.
In that regard, it's actually a good thing that the adventure is mostly combat-based, because that's the systematic and mechanical part of learning the game - the bit that the Starter Set can teach in a controlled manner, and the bit that a new DM can practice, and practice extensively, in order to become a better DM.
And if, on top of the combats, the adventure also provides guides for roleplaying, even if these are rather minimal, then that's a
fantastic thing - not only does it teach the systematic elements, but it also makes clear that there is something
more out there. That's actually better than the adventure in the classic BD&D "Red Box" did!
Basically, I don't think this adventure
is "the foundation of a new edition". It's a teaching aide for new DMs. For "the foundation of a new edition", the adventure you want is "Tyranny of Dragons".
(Oh, as for my own opinion of Phandelver, I don't have one, other than not liking the name. I've been reading the "Firefly" and "Doctor Who" RPGs, so haven't had chance to get to 5e yet. Give me a week.
)