I've just finished with Digimon Survive after completing the Moral and True endings.
Despite a lackluster battle system and some points where the story got too repetitive or awkward or slow, I really enjoyed my time with the first playthrough -- Enough to watch 2 more endings online (in ultra-fast-forward) and play through the true ending myself.
The true ending featured some additional party members I ended up really liking, but dragged on far too long.
While I'm glad I played the extra ending for closure and for the warm fuzzies in the final scene, the true route really lacked any additional character development in chapters 10-13 -- in a story about the characters developing.
Since the whole visual-novel half of the game is built around talking to people and raising affinities, this results in several additional hours of repeatedly telling Kaito he's a good brother and telling Aoi she "has really grown" while being force-fed a bunch of not-really-canon digimon lore.
The 3 non-true endings are definitely the more interesting routes, though they have a lot of overlap (and don't feature my favorite character!).
But enough about the story, I came here for the Digimon!
There's quite a few Digimon to collect via recruitment in random battles and via your party 'mons evolving. Those attached to humans evolve with the story or once your affinity with that human is high enough, while recruited digimon are evolved with items
The recruiting mechanic is absolutely stupid, but once I started using a guide it was fun collecting and evolving lots of 'mons. I used another guide to minimize overlap, as many of your party's fixed final forms can be obtained through random recruits.
I did find it odd that many party and story digimon could be obtained through random encounters (+ evolving). It's a bit awkward when the story has a powerful digimon appear and threaten the fabric of reality... and you've already got the same 'mon in your party.
Likewise, it's a bit weird to have WarGreymon show up in a random battle and be recruitable by responding correctly to a query about nap preferences... There's lots of questionable decisions on the recruit mechanic.
Complaining aside, if you grew up loving digimon and enjoy the occasional visual novel, this is one of the best-looking visual novels I've played. While the story is about as deep as a kids-show about digital monsters, it's worth at least one playthough for nostalgia's sake.