I finished Mana Khemia last night (with Nikki's ending) just shy of 75 hours. It was... okay. It felt almost exactly like Iris 3, although the synthesis seemed a bit better; not to mention Flay reused Edge's sprite. Honestly, Mana Khemia felt more like a sequel to Iris 3 than Iris 3 did to Iris 2. And having played the Dusk games first, it was awkward hearing Keithgriff voice three different characters, as his older, gruff voice (and stiff acting) didn't fit the younger characters.
Few things I didn't like. The day/night cycle was awful. Enemies were way too powerful during night time for zero added reward. I just ended up standing around waiting for nighttime to end, which kind of sucked because I was streaming while I played. I had the same issue with platforming segments as I did in Iris 3. The lack of a shadow for the character sprite makes it excessively difficult to judge trajectory, and having to jump across one-tile platforms with the isometric perspective is an exercise in frustration. Also, the game screws you on money. I got straight As on class assignments and did every job board quest, and at the end of the game, I still had to spend about 4-5 hours grinding for money to buy materials. The amount enemies drop is pitiful. The post-game dungeon was pretty terrible, too. Enemies do 5x damage (which basically kills my characters in one or two attacks), and I can only damage them with critical hits. After spending about 20 minutes on one random encounter, and only killing two of three enemies, I said screw it.
Overall, it certainly wasn't a bad game by any means, but I didn't really get attached to any of the characters like I did in the Dusk or Iris games, and I don't particularly care to go through it again multiple times for different characters' ending. I'll be moving on to Mana Khemia 2 tonight with an Ulrika play-through.