One of the things people will notice almost immediately is how the storyline is structured. In the original Digimon anime, the seven children meet and get their Digimon right away in the first episode (with the eighth child joining later). Not so with this series. No, in this series, it takes some time for them to meet. In fact, it's 20 episodes before Takeru (T.K. in the dub) even gets his Digivice.
Another difference is the way the evolutions are paced. There is almost ALWAYS something new for the characters' Digimon to do in each episode. Digimon will get the attacks that they had in the previous anime, but they also get new ones, like MetalGreymon's rail gun. Speaking of evolutions, the first two episodes essentially are a remake of Our Wargame (the first half of the Digimon movie in the dub), and Omnimon/Omegamon shows up in the second episode. So it's kind of like the show is saying, 'This is what's possible'. But the thing is, after that episode, we haven't seen Omnimon since (it could be because the children are split into two groups right now, and of course Taichi/Tai leads one group and Yamato/Matt leads another).
The animation is for the most part really good. The show doesn't use as many stillframe zooms (characters moving from the foreground into the background without any animated movement) as the original did. And the evolutions look great. They don't just spin and BAM, Digimon. They're way more flashy and involved now.
As for the music, the original composer's presence is definitely missed, but the music they do use still works for this series. It makes the show feel like something new, even despite it being a reboot.
Not too much more to say yet, since I haven't finished the series and it's supposed to be 66 episodes long. But as of right now, so far so good.