Frontier was the first Digimon I experienced the original version of, and it just seemed so much cooler with the neat opening theme, the insert song, etc. So it sort of holds a special place in my heart, and I liked the return to a more adventurous Digital World after Tamer's wasteland. The characters were solid, too, even if they sort of borrowed a lot of characteristics of the past humans.
I also thought the "becoming Digimon" was pretty neat, and once you got past no partners, it was an interesting premise. Unfortunately, it pretty much broke down once the Royal Knights showed up, and everyone but Takuya and Koji were shafted. I mean, giving them exclusive forms, I get that, but literally making it so the other characters couldn't Digivolve was ridiculous. It was also disappointing that the other Spirits like Grottomon and co. never were brought up again after being defeated, even though they introduced other human characters and sort of teased it. And Koichi was a pretty wasted character too I recall.
I recall the dub being quite nice, the new OP and Digivolution themes were a little more mature and less goofy, and I loved the episode that shows Koichi's past, and they used a really neat insert song.
I sort of hope if Adventure 3 does good, they take a shot at another original Digimon Series that's somewhat in the vein of Frontier, sort of a classic take on the franchise with some interesting elements to it.
