Just finished my play-through of the trial version. While I did not finish KiraKira, based on what I did play, Overdrive kicked it up a notch. I only played until the intro played--which was rather long as it was--but that was enough. Bought.
The OST is great and helps to set the mood of the story. The art, cg, and character designs are much improved from KiraKira. One of Yayoi's sprites looked weird to me, but otherwise it's very well polished. Even more than KiraKira, the Deardrops trial did not feel like I was playing a visual novel. It's its own unique story.
Anyway, regarding the characters...
Shoichi is an interesting protagonist. He's stubborn, uptight, and started off a bit emo. However, he's also insanely passionate and dedicated when he decides to accomplish something. It's clear that he's not going to let whatever it was that killed his career as a violinist stop him from moving forward as a guitarist. I like the fact that he's an adult.
Riho is... I don't think the term "tsun" even describes her behavior. Well, the introduction set her up to be quite unlikable, to put it nicely. Until the very end, where it you start to understand why she acts the way she does. I can definitely see strong character growth in Riho's path--particularly in regards to interpersonal relationships. And being the main heroine, I'm looking forward to it!
Eiji is basically the complete opposite of Shoichi. When he was first introduced, I couldn't stand the asshole (don't litter!). But one of the things I love about the Deardrops introduction is that the story compels you to love its characters after it teaches you to hate them. Sure, Eiji's a bit rough around the edges and bad with people, but he's basically a good guy who takes his music seriously and expects the same of others. Eiji's awesome.
Kanade is a pretty standard osananajimi and also strongly my type. I like that fact that, like Shoichi, she's an adult. Sadly, she didn't join the band and was relegated to being a cheerleader during the introduction. I hope this will change as the story progresses, as it would really suck if her story had no relevance to the overall plot. With that said, I think there is more to her than being cheerful, supporting, and having a pinch of jealously. When Shoichi mentioned that she hadn't changed at all, Kanade mumbled it was because she couldn't change. Perhaps I'm reading too much into it, given my luck with the girls I like the most having the shitiest scenarios.
Yayoi is my second favorite character. Her normal personality is serious not all that unlike Shoichi. But when it comes to guitar, she's bat-shit insane--and fantastic.
Rimu is well, Rimu. Her part of the intro was the only part I felt dragged on too much. After the intro, I'm struggling to see where her story could go now..
Chika is the best side character in visual novel. I love her cheekiness. Honorable mention to Kanako-sensei. Fan girls everywhere understand your pain.
Planned order will be Yayoi --> Kanade --> Riho.
Clannad is Life, Da Capo is Pure Love, Higurashi is Ethics, & Tori no Uta is the National Anthem.
The ones who will have the last laugh are the earnest and the honest.