I've been playing heavily, and until I finished the main story yesterday have mostly been avoiding discussions online. I've completed all main story quests before finishing the game, and I definitely enjoyed the game a lot.
A couple of generally low/minimal spoiler thoughts:
I find it surprising just how much from BotW was reused. The only other time they've done that in a major Zelda release was Majora's Mask, which was produced in a very short timeframe (about 2 years) - and even that had a totally new world it was set in even if assets and mechanics were reused. Here, basically the entire core structure of the game has carried over from BotW. Combat is basically the same. Ground level map is broadly the same, the story structure is very similar (go to 4 main areas, which are the same four as in BotW, also find Zelda's memories through a picture based mechanic), there's still the same Shrine system and Koroks for upgrading etc. I guess we always knew the game would have a lot in common with BotW but I'm surprised just how much it is.
TotK definitely feels a lot harder than BotW to me! I think it's a combination of there being far more enemy variety and most returning enemies have more attacks, plus things like the Depths is especially tricky early on due to the temporary max health reduction. Also several more subtle things, such as Hearty food being much rarer (RIP Hearty Durian farms in Faron), armour being more expensive to upgrade - and buy, actually, since rupees are far tougher to get. With that in mind, I found myself wanting to upgrade max health far more often than I did in BotW. In BotW I'd often get max stamina before even taking a 4th heart - after all why bother when I can make a few +15 max heart meals and take minimal damage due to upgraded Hylian Armour? But here, a combination of the Depths making max health more valuable, plus stamina being less vital due to many other ways to gain height, plus less Hearty food, all make heart containers more important.
The dungeons in TotK are MUCH more fun than the BotW ones. Each has their own aesthetic, and several of them feel much more like classic Zelda dungeons with central gimmicks and a semi-linear intended path, which makes for a really enjoyable experience. I'm sure you can also just totally break the dungeons if you want, but hey, that's fun too. The bosses are also more interesting than just Xblight Ganon over and over again.
On the topic of bosses, the final boss fight is really well done. There were several things in that fight that caught me off guard in a good way. MAJOR spoilers I guess here:
1: Ganondorf literally destroying heart containers. Makes perfect sense as he already did that in the Prologue, but still when I realised I wasn't just having hearts gloomed
but literally removed it was like, oh crap, I can't stall this forever
2: That health bar. It's a bit cliche maybe but it worked.
3: He flurry rushes you and even dodges during your flurry rushes. Really just highlights how much of a badass he is.
4: I somehow didn't see the demon dragon transformation coming. Final phase was mostly just for show, but works as a climactic finish far more than Dark Beast Ganon did in BotW.
I'm so far not entirely sold on the Depths. I think it's a cool concept but I think two issues I've picked up are that 1: It feels unrewarding to explore (especially as it's the "hard" area to explore), and 2: it feels a bit too empty and devoid of content.
For point 1, generally I just feel like you can spend a whole lot of time there and not have much to show for it. I probably spent about 10 hours in there yesterday and today, and all I have from it is like 20 extra battery charges or so, plus a few schema stones and cosmetic items. Nice stuff, sure, but I feel like I could have gotten far more of value from the overworld or sky. As for point 2, I feel like you end up just running from key point to key point in the Depths, found from your map - or just fly across them where possible.
That said, I do like the idea. I've seen some people compare it to the ALttP Dark World, a vertically mirrored version of the BotW map (approximately) which is nastier to explore. I find that a cool concept, just I think it could have been a bit more enjoyable execution wise.
Overall though, really enjoying the game. There's a ton of stuff to do, and even though I beat the game yesterday I'm still completing Side Adventures, Quests and Shrines and expect that'll last me several more weeks yet.