I had a lot of fun with this game. I wouldn't say it's as great as other people say it is but it's definitely well above average.
The plot was OK but pretty predictable most of the time. I liked how they would point out obvious plot points instead of making them try to seem surprising when they get revealed. I'll admit that I was pretty surprised when I got that bad end halfway through the game. I went online to see what I did wrong right away instead of just playing my file again. Since there wasn't any choices to make in the first half I thought I might have made a mistake during one of the battles.
Probably the thing I hated most about this game was that they waited so long before letting you pick one of the other girls. They don't really get their own routes and your relationship with them feels kinda forced. I think the game would have been much better if they let it branch off into multiple routes.
I also didn't like that Arata wasn't voiced. The seiyuu for this game were great but it just felt incomplete without Arata having a voice (especially when he was suppose to be talking at the same time as someone else but all you hear is the other person).
The characters were pretty good, though I liked some of them much more than others. My favorite character was Lun Lun, which really surprised me. While I'm a fan of moe characters like her, I usually prefer characters like Chris or Shizuka. I can't seem to think of a single thing about Lun Lun that I didn't like. I loved her cheerful personality, her voice was adorable (I loved how she pronounced her name and I must have replayed it about a hundred times when she said "Stop! Time! Wait a minute!"), she had great interactions with the other characters, she had a good character design, and I thought her dress design was perfect for her (it was cute yet it still had a strong feel to it). While it doesn't bother me too much, I do wish that her real age would have been revealed (unless it was and I missed it).
My second favorite character was Chris. I really like girls that you can be good friends with and I love tomboys (and reverse traps). While I loved that Chris tried to act like a boy, I felt that she went too far. It's made clear why she tries to be a boy but I really don't like it when characters lie to themselves like that (especially when Chris still tries to make Arata think of her as a boy after he finds out her secret).
Out of the rest of the girls, I would say that Suzushiro is my third favorite. I really liked her character design (especially her dress) and I think Goto did a great job with her performance (though I had a hard time not laughing whenever she yelled out "Shihou!"). I really felt bad about her relationship with Chris and wonder how it turns out after the game ends (especially when you pick her).
I felt that Arata was a pretty good main character though there wasn't anything that memorable about him. I liked Shizuka, though I think she didn't get enough attention (her growling also got on my nerves). Angela and Liesel really didn't appeal to me that much (which is kinda disappointing since I even liked secondary characters like Pigeon and Crow more than them). I really wish Nodoka got more attention.
The sprites were definitely one of the best parts of the game. They really made the scenes much more entertaining. While the sprites were used very effectively, I didn't like the lack of battle sprites. It got on my nerves when the characters were suppose to be taking a lot of damage in battle but yet their sprites looked completely fine.
The card system was pretty fun though I wish you could have battled more of the other princesses with it. It got pretty dull just battling the same few enemies over and over again.
The h-scenes definitely seemed forced, though not as forced and out of nowhere as some VNs. I also thought Arata's penis seemed awkward and unnatural. It made me wonder how much experience the artist had drawing that type of stuff. I also didn't like how much the girls bled when they had their virginity taken. It seemed like way too much, even by hentai standards.
Also I found the CG for the scene where Arata was hugging Suzushiro to look incredibly awkward (it was suppose to be a serious scene right?).

I'm really tempted to make a Shoop da Whoop out of that pic.
It also reminds me of this.