This is actually my second time playing this VN, though my first playthrough only went through Neko and Kohane.  I will say that playing this after the original series does change my perspective somewhat, as it is easier to get the many references throughout the VN.  Hakari, one of the heroines, is the cousin of the protagonist from the original trilogy and the protagonist is Kani's cousin.  Jiro is a relative of one of the Kenpou Club's members from the time of the first protagonist (ten years before), Cherish is the daughter of one of Serebu's father's friends, Kasumi's family is served by the Kurogane family (Otome's family), and Neko was raised in an orphanage that came to be owned and run by Sunao's father.  In addition, one of Murata's little sisters is a classmate of the new protagonist and... well it goes on like that.  In other words, it is hard to fully appreciate this game without playing through the original series, which is probably why I ended up being so bored with it the first time around.

Common Route

To be straight out, the common route is pretty hilarious, in a style that is almost equivalent to that of the original series, though the new character dynamics are quite a bit different.  For one thing, the 'group of friends' is a bit looser than in the original series (in the original, it was a really tight friendship, like a family), and the school's situation is a bit different.  Hakari, who is the Student Council President, is a natural manipulator and a genius, but she lacks Erika's hedonism and charisma, so she generally controls things from behind the scenes.  This is opposed to the hard-headed Morals Committee, which is led by Neko, who is obsessed with rules and whose ideals just don't match with those of Hakari.  This is a source for most of the conflict in the common route, and it is generally amusing.

Neko

I can't say I've changed my opinion of Neko's route.  Similar to the original Otome route in the original Tsuyokiss, it is a surprisingly weak route for such a character that leaves such a strong impression.  For better or worse, Neko is a bit hard-headed... like Otome she is ridiculously strong (both of them are about .8 of Momoka from Majikoi in terms of strength), and she is a stickler for the rules... but in exchange, she is ridiculously cute once she falls in love with the protagonist (definitely went for gap-moe here), but there is a severe and unforgivable lack of drama in this route, despite some foreshadowing.  I think that they intend to use Festival to give that foreshadowing life - and probably intended to from the beginning - but it makes for a pretty frustrating experience.

Hakari

The protagonist's osananajimi, the Student Council President, and the original Tsuyokiss protagonist's cousin.  To be honest, her route has the same problem as Neko's.  It sticks to a very simple love-comedy equation and doesn't go into any of the down and dirty that frequently framed the background of the original trilogy.  For that reason, I can't help but give this route a reluctant thumbs-down.  I'll be perfectly honest... this VN is starting to remind me of Nigakki for the crappy heroine routes.

Cherish

Cherish (also known as Cherry) is the granddaughter of a former American General.  Her personality is bright and straightforward, and she is the game's 'bakaloli'.  Her path is a bit weird, in the sense that she and the protagonist never quite fall into the conventional 'lovers' slot, where both sides are passionately in love.  Generally speaking, in VNs when a friend makes the transition to lover, there is a bit of tension and drama, but in this case it simply doesn't happen.  To be honest, even after the six hours of this path, I had to ask myself if she was a heroine at all (despite the kissing and sex scenes).  Like the other paths, hers lacks any significant drama.

Kohane

Kohane's role is a lot like Nagomi's in the original series.  She starts out as a delinquent-like girl and once she goes dere, it is the most extreme of all the heroines in contrast.  Also similar to Nagomi, it is the protagonist sticking his nose into her circumstances that eventually results in them becoming close, though there are some significant differences both in degree and detail.  Kohane is easily the best of the four heroines available when you start the game, or so I've concluded after having played those four routes.  However, like the other routes, it ends in a way that makes it feel incomplete.  I have to conclude that this entire VN was designed to make way for Festival.

Sumika

... well, here is definitely the true route of the VN.  The difference in detail, quality, and overall everything between it and the other routes is even worse than Majikoi's true route.  Sumika's route basically brings everything that never quite came to fruition in the other routes to the forefront - including cameo appearances from Otome and Kinu (Kani).  Sumika grows a great deal across the path, and it is easily the best path in all the Tsuyokiss games so far... but in exchange, it has sent me into a screaming rage.  Why?  Because all the other heroine routes were so weak, probably precisely in order to make Sumika's route strong.  I absolutely hate it when a company deliberately weakens other heroine routes in order to make the true heroine's route stand out.  In this case, it was rather extreme, considering how stand-out the heroines were as characters.  So, though I went ahead and adjusted my vndb vote a bit upwards, I nonetheless do not feel good about this VN.  Hopefully, Festival will rectify the crime that is this VN, and thus make me happy, lol.

Edit: In terms of raw quality, while Sumika's path is better than any one Tsuyokiss path in the previous games from a pure drama perspective, the sheer atmospheric gap between it and the other paths, as well as the fact that the paths were generally left improperly or unresolved, meant that I honestly couldn't enjoy it as I would have if it were just one path amongst the others.  For this reason, I can't help but condemn Candy Soft for doing it this way.