It's okay. Some of it I enjoyed, while other bits were bland or a bit dull. That said, though, I watched it all the way through and became moderately attached to its characters. The battle scenes are a problem, but I like the fact that a lot of the show is just character-based.
Firstly, Digimon. It's a classic kids' franchise, appearing a couple of years after Pokemon and doing something so similar that everyone compared them at the time. (The main difference is that these child heroes can only have one Digimon, thus tying the show more firmly to that one-to-one relationship than the Pokemon kaleidoscope of "gotta catch 'em all".) "Digimon" means "Digital Monsters", which in the real world were originally launched as virtual pets, like Tamagotchi. There have been lots of anime series, but this is a sequel to the first two: Digimon Adventure (1999) and Digimon Adventure 02 (2000).
I was intrigued this idea. Digimon is normally another "tiny kids have loud adventures" kiddie franchise. Here, though, those tiny kids have been allowed to grow up. It's the same heroes we saw in 1999-2000, but now high school students and thinking about exams, college and girlfriends. At the same time, though, they still have those goofy-looking Digimon partners, drawn to look as if Disney got drunk.
To be honest, I should have probably just watched the original shows. Fans of the 1999-2000 anime aren't too keen on this sequel, as far as I can tell. However these things tend to run all year round, which is a big time investment, and in any case I was interested specifically in the juxtaposition. A kiddie show, updated to be non-kiddified but still preserving its most important qualities.
The cast are fine, apart from the bland character designs that make them look indistinguishable and/or boring. (Some people have said it's an upgrade from the original!) Nonetheless I quite liked them. They're not super-interesting, but I liked stuff like Mimi returning from America and getting genuinely upset when she tries to help with her school culture festival and finds that her enthusiastic, forceful personality is rubbing up her classmates the wrong way. Joe just wants to study, which can create trouble. Apparently the show's creators think Hikari has unsisterly feelings for her brother Taichi. (You'll have to wait and wait to see any evidence of this, though.)
However the strongest relationships here, by a million miles, are the human-Digimon ones. Everyone has one Digimon and they're very, very close. This is clearly the best thing about this show. Not everyone initially accepts it, but eventually they'll be embracing their love for a goofy cartoon character. (Mostly. Exceptions to this can be genuinely shocking.) This is further strengthened by, personality-wise, the Digimons being children. That's explored very well and I really liked it... although browsing wikipedia told me, to my surprise, that canonically the Digimon Adventure 02 epilogue said that Taichi would have a son with a Koromon. This is, um, wrong. Love for a Digimon shouldn't go in that direction. Fortunately more googling clarified that ambiguous sentence, so now I know that Taichi's future son will acquire a partner Digimon and that that will be a Koromon. Whew.
Is this a bad show? No. I quite liked it, but it's a bit of a pudding. The word is "okay". The fight scenes are almost always dull, partly because the humans can't participate at all and partly because they're full of Digimon shouting "super-evolve" and having Monster Transformation Sequences. I approve of respecting the original, but too many of those would get me hitting the fast-forward.
Similarly the plot isn't going anywhere fast, isn't very good at tidying up after itself and is at its dullest in the last few episodes. There's a god-figure (Homoestasis), an occasional baddie and (for me) a muddiness that I bet comes from being rooted in show lore from eighteen years ago. I was surprised by the ending, though.
Would I recommend this show? Nope. It's not good enough to justify its 26-episode length, unless you're already looking for it (e.g. you're a Digimon fan). However it's quite likeable and watchable enough, if you're willing to take a bit of rough with the smooth. Every so often you'll discover that it's willing to play harder than you'd think. Death is an option. It also has a cool theme song, which it exploits strongly enough to make even a complete newbie (me) experience phantom nostalgia. It's probably not quite what you'd have been hoping for, no matter who you are, but it has a heart and some good bits.