This is a very highly polished portal experience. The puzzles are mostly pretty easy but not totally trivial. The plot is fine if not up to the hilarious high standards the portal games set.

My main criticism is that there is a lot of walking around aimlessly through environments between puzzles. Obviously they put a lot of time and effort into those environments but they added 0 to the fun of the game and just padded the game time. There were even several times when it wasn't obvious where to go next that I spent fumbling about just lost not even in a puzzle not even using my portal gun.

I also have one minor quibble about the last few puzzles that I won't elaborate on so as to avoid spoilers, but suffice it to say I had to redo parts of that puzzle that I had already solved many more times than any other puzzle before it.

Obviously it was amazing in a lot of ways.  The new abilities are way more fun than BotW, the story is definitely stronger than BotW, the puzzle design is way better than BotW, the overworld design is much more interesting, there seems to me to be less useless filler.  Someone who likes open worlds will want to explore every inch of this place because it is so well done.
It definitely has some flaws as well though. Weather is perhaps explained slightly better but still sucks.  Rain and lightning especially are awful and add nothing to the game but frustration. Upgrading armor is a super important part of the game that is basically completely opaque.  The questline required to fully upgrade your armor might as well require searching on the internet.  There were a bunch of shrines that were "transport this crystal back to the shrine" quests that were sometimes fun but usually super tedious.
While the main land has been vastly improved, the added sky and depths areas are sorely lacking.  The sky area is great at first until you realize that it is mostly the exact same area copy pasted about 10 times.  The depths has some fun enemies / mini-bosses but is mostly a vast emptiness made worse by the annoying gloom mechanic and darkness requiring you to constantly throw or shoot little seeds to light up the way. Tediousness is not gameplay.
Some of the controls are weirdly clunky.  Trying to run or jump while crouched doesn't work until you uncrouch. You have to run to put away your weapon otherwise the shield button does nothing. There are a bunch of times I can no longer remember when I thought things should work one way and worked another instead.  Also, switching between powers was weirdly slow, I couldn't just push the power button and the direction and instantly get the new power.  I had to hold the power button for a half second until the power menu came up and THEN I could point a direction to switch powers.
The open world does not do any favors to the progression of the story.  Because you can do stuff in any order, they re-explain what is going on about 15 times.  There is one long major cinematic that is repeated almost verbatim 4 times in the game.  It is so identical it feels lazy.  I did a series of quests to get a bunch of background story and that ended up being basically a waste of time because all the interesting bits were called out later about 5 more times in other story parts.
Overall, highly recommended but definitely flawed.  If you like open world adventure games, it may be the best one ever made.  If not, ymmv.

It was better than I expected. I had read that it was more like a demo than a game and took less than an hour to beat. With those expectations I still bought it and was very pleasantly surprised.
The mysteries were interesting, the mechanics solid, and it took me almost 3 hours. There were some annoying spots where I got stuck on mechanics I didn't understand or contradictions that I either tried at the wrong time or that didn't seem like contradictions at all based on my reading. All in all though, I am glad I tried it.