Currently done with Chihaya's route (was planning to do Chihaya => Akane => Shizuru => Kotori => Lucia, but since you have to do kotori before Shizuru, I will have to swap both).
My initial impressions are currently positive, not as much as I would expect, but still better than the impressions of LB regular routes.
That being said, I must say I'm quite disappointed in term of the production value here, as Key was a tad stingy with this special project:
I know it is a common trend with VN, but Kotarou being not voiced is a huge issue in term of immersion whatsoever. He is probably the protagonist among all key games with the most excentric personality, yet not voiced (I don't buy the "player being able to identify themselves with the protagonist" excuse for ages, and it certainly won't work here).
That is to say, random high schoolers, punks etc being not voiced is also an issue on the long run, especially during the common route, where it occurs quite often that we get only nameless grunt and Kotarou "speaking", leaving a huge silence gap as result... (and for some reason, people like the camera guy or Inoue being voiced are the exceptions).
The other production issues I've noticed here are... the BG and CG.
The BG are basically not smooth at all: of course, they are more detailed than say LB, but the impression from them is pretty rough (and the large base resolution of the game doesn't help). You can actually discern the 3D modelisation far easier than previous Key works for some reason. And they are quite empty to boot (for instance, they went back to empty classrooms, despite they were at least "filled" in clannad and LB).
Meanwhile, I have no major problem with Inoue art, and it is more consistent than before (except maybe most of Chihaya's sprites), but while reading Chihaya's route, I felt that route (and probably the other ones) needed much more CG to describe the events exposed by Kotarou. In a way, the narration wasn't really complimented that much, due to the very scarce number of CG, leaving some sort of weird impressions (the very last portion of the route with Philosophyz playing is the most evident issue).
I can see they made a lot of efforts with the special effects (Kotarou VS Yoshino, and the ESP moments being the prime example of it), but on the other way around, they neglected quite a lot in term of BG and CG, which is such a pity, since these are much more predominent than the special effects, obviously (at least, Aurora effects weren't cheap looking).
That's as far as I would say regarding the production value for now.
Regarding the storytelling so far, it is definitely different from previous key stuff, but the structure is still recognizable.
The genre shift is much less brutal than I would expect for now, so I can't say I have any complaint about that.
That being said, the common route was really long... perhaps a tad too long to be honest: I have no idea if it is because they didn't fill the "action less" portions with too few humor or so, but sometimes, I felt that really "nothing was going on", several times. Nothing really that major, but whereas it was sort of eventful with Clannad or LB common route, Rewrite common route pacing was a bit bipolar (sequences between fun time / creepy, mystery were bit bland), but that lack of balance is fine, especially it gives a huge contrast when Kotarou is facing abnormalities.
As for something more in depth:
Spoiler for Chihaya's route:
I was sort of surprised that the plot was more or less similar to X by clamp. It was difficult to have the full grasp of the situation considering how everything was focused on Chihaya, nevertheless, I'm curious how things will go with Akane, considering her position among Gaia.
I must say the whole struggle between Gaia and Guardians wasn't as intense as I would expect from this kind of conflict, but at least, some foreshadowing stuff and consistent details were present not to make the whole deal completely over the top.
I was however not so impressed with the romance and how it was handled: thankfully not completely abrupt, kotarou falling in love with Chihaya was a tad too fast though. I think they went a bit too overeager with the supernatural exposure and forgot few more [galge like events/flag] to lmake the transition better between the two, especially when you consider the fact that Kotarou had lingering feelings for Kotori, even now.
That being said, I was afraid of a very cheesy end, especially after Sakuya was actually the last dragon "boss", but thankfully, his time was up still. They didn't forgot about some fundamental things and somehow managed to lay grounds on various points that should appeal the readers interest (the true nature of Kagari, Akane's motives, etc), which certainly explains why you have to go through Chihaya's route before Akane's.
Overal, Chihaya's route was a bit convulated with few interactions, but was surprisingly intense, especially during its last third portion, which certainly lives up with the exceptions from the second opening.