So I just finished 100%'ing Age of Calamity today. Overall, I'd consider it an 8.5/10.
The story definitely went in a different direction than I expected, but it was still enjoyable. The cast is smaller and less varied than HW, but it makes sense given HW was basically a Zelda crossover, while Age of Calamity is effectively BotW Warriors. That said, they still had plenty of characters who I did not expect, so there were plenty of surprises in that respect.
On the negative side, having everything accessed from the map could be a little cumbersome at times, as I sometimes found myself wishing for a more consolidated setup for character upgrades. Combat did have some dips in frame rate, especially during certain effect-intensive attacks, but it wasn't enough to take away from the experience as a whole for me, given I didn't have issues of enemies failing to load or anything like that.
Gameplay-wise, it's definitely like night and day compared to HW. Although they're both Musou at their core, Age of Calamity definitely has a higher skill ceiling and needs more involved technique. Rather than just hold guard and spam dodge until a weak point or item prompt appears appears, you can utilize Flurry Rushes and parries to create openings if you're more willing to throw yourself into the fray. Enemy density was a lot lower, given enemies numbered in the hundreds rather than the thousands, but it seemed like enemy quality was higher to compensate. Even generic mooks could be threatening, such as elemental Lizalfos spitting ice/fire/thunder at you while you try to fight a stronger enemy, or horn-blowing enemies commanding all of the mooks to attack in unison. If you're looking for a mindless, cathartic game like original HW, this definitely isn't it, because you'll be taking a lot more damage if you're not careful.
I did find it strange that they opted to do away with ranking entirely for non-story missions, given both HW and FE:W utilized them. But it did take away a lot of the stress, and it's nice not having to re-do a mission because you took 6 seconds longer than it wanted you to or something like that. Just complete the side missions, and you're good.
It had about 60 hours of content for me to 100% it, which wasn't a bad amount. It doesn't have the endless adventure modes of original HW, but this is not in and of itself a bad thing because those could get a little repetitive at times. Plus, most of the additional Adventure Maps in HW were DLC, so in terms of the base game, I'd say the amount of content is acceptable. We'll see if/when there's DLC and if it adds more content. If nothing else they mentioned the digital pre-order spoon bonus would be available as DLC.
Overall, it may not have been a perfect game but it was still very enjoyable, and the challenge made beating it more satisfying than I expected it to be.