I've just beaten Comrades, I have 13:05:53 spent on it. It was a lot of fun, and engaging, more so than the main game itself, and I enjoyed it, and now, Episode Ignis remains, and I'm even more excited for it. I enjoyed Comrades' game-play, I hope they implement some of it's elements into the main game, too, but I doubt that'll happen. As for how I rate the major DLC so far, here's my scores.:
Episode Gladiolus: 6/10: It was fun, but the game-play was slow, and it's story didn't help appreciate Gladiolus and character to me.
Episode Prompto: 8.5/10: I had plenty of fun with this, the open area, and especially the music fit the tone of it in regards to Prompto and his struggles, and managed to deliver a proper reveal of the twist he had in Chapter 13, and developed him further as a character, and how he got into Gralea held in the Keep to some degree. The game-play was solid, but the controls were a little confusing.
Comrades: 9/10: See my thoughts above.