Glad you enjoyed it! It sounds like Meruru improved on a lot compared to the other two Arland games.
As for me, I've gotten started on Hyperdimension Neptunia Rebirth 2 and reached the second half (?) of Chapter 2 (reached Lowee, met and fought Ram and Rom). Some first impressions: The good: The environments look better than the first game, I find. They're a tad bit more colorful and varied. I also enjoy the neat sound effects they added to fit the environment, like the bird chirping in Virtua Forest or the sound of the waves crashing in the resort areas (because apparently, Lastation has those now). Nepgear and Uni are adorable, even if Uni is practically a younger-looking Noire, but with a gun. I get some Atelier protagonist vibes from the way Nepgear is characterized. Now I seriously wonder how she and Neptune interact, considering they're practically opposites... The surprising: There seems to be no continuity between this and Rebirth 1, considering the world map looks entirely different, IF and Compa claimed to have known each other since they were kids, didn't recognize Falcom, who looks completely different now, didn't recognize Puchiko Broccoli, the four lands have Oracles now, who help the CPUs run the place (Histoire got a serious downgrade with that, from a basically all-knowing tome to what amounts to a secretary), Avenir apparently never existed, considering the new origin story of the Killachines, and of course the biggest one:
Then, there's the fact that things seem to be a tad bit more serious than in the last game, considering it starts with the CPUs basically dying. Then again, there's that Star Wars-esque text crawl that - among others - points out that "Things are messed up, you guys", so the humor is definitely still present.
Another thing: For a supposed "younger sister", Nepgear sure looks older than Neptune. I wonder if that will come up. The slightly worse than the first game but not so bad that it's a dealbreaker: I preferred the aesthetic of the world map in Rebirth 1. It's not bad in this game, far from it, I just loved the islands floating in the sky thing the first game had going. I also found the CPUs to be more immediately likeable than the Candidates. In particular, I don't think I am that much of a fan of Ram and Rom yet. I also don't know how to feel about Red, whom I'm convinced is supposed to be a parody of the "hardcore waifu crowd". Nepgear also feels a lot weaker than Neptune in combat. When I compare the damage output of Neptune's Cross Combo in the first game and Nepgears initial SP skill (the name escapes me at the moment), Cross Combo did a heck of a lot more damage. This also holds true for their respective HDD transformations. Purple Heart felt a bit more powerful than Nepgear does. It makes sense, however, since Nepgear is only a CPU candidate and not an actual goddess, but it's something I've noticed nonetheless. I do appreciate the fact that Nepgear comes with a defense buff and a healing move, the latter of which the CPUs from the last game sorely lacked.