The shifting from having Digimon partners to turning into Digimon isn't a bad thing.
True that's a great change, but once one thinks about it- it's actually pretty cool. This method of Digivolution actually puts the children into the battle, putting more at risk and making the fights just a bit more interesting. True that Tamers did it first- and in a better way as it involved the kids actually fusing with their partners to become one- but Frontier was a new season and that meant that the writers wanted to take something new and run with it.
The show in general has rather average animation mixed with great voice acting. One can easily see that there are two different art styles used and it switches in between episodes, with one being used more than the other. Stock Footage is clearly abused, but there are a few fighting scenes that are worth watching, but there are also fights that seem to either draw on, or there isn't enough movement, and to be frank most are predictable. On the other hand, the voice acting is great- especially since the dubbed version uses voice actors such as Michelle Ruff, Steve Staley, Crispin Freeman, and even Daran Norris.
Where the show falls down hard though is the plot. The first half of the show was decent- saving the Digital World. Sounds simple enough. A few episodes were fun, the characters are entertaining in their own way, and plus this season has one of the most complicated and compelling family conflicts in Digimon history.
The second half though was just awful. When we see the new villains The Royal Knighs, and hear about Lucemon- we expect more from the next 10 or so episodes rather than the same battle over and over again. Which is what the second half is for the most part- the characters use their new ability to turn Takuya and Kouji into their supermode forms in order to fight the same battle that we all know they are going to lose. Not only is the absence of participation from the other characters not fun, but neither are the repetitive battles. It isn't until the end when the fights become interesting again.
The season itself is not perfect, but if you're a fan willing to give it a chance- or someone who just likes the character designs-it's worth a try. Though once you reach the Royal Knights, just skip a few episodes if you don't want to bore yourself.