Uh, minor caveat: I haven't posted to LJ in forever so if I screw up any of the htmling, that's why.
Firstly, what annoyed me greatly about the drama CD's is that there is paucity of information on them, period. Other than the summaries on Lena's page about the contents of what's going on, and what my own ears can pick up, I really don't know what the heck is going on. AudioWiki has even less. That means no translations, and thanks to the brand spanking new cast, I get confused who's who, because I'm not familiar with these voice actors in the least. *blushes* (I'm not a big follower of any seiyuu.)
Generally speaking, I would say these new drama CD's follow the rewritten novel. (I've listened to the Shiozawa Memorial recently, and I'm trying to guess when they made that. It was released a few months after Shiozawa's death, so I'm guessing that it was some leftover material they had from when they were making Dark Erogenous. Hmmm...mainly because they had different voice actors for everyone excluding Shiozawa, and Seki Toshihiko for Riki.)
The summary for Destiny, the first CD, was particularly sparse. I'm guessing it's the period before Riki's captured because track five of the first CD is definitely that first scene where Iason catches Riki pickpocketing.
I have to say, just like the novels, the interpretation that Toru Okawa does for Iason fits the image much more closely of novel Iason than the old OVA. It's a great deal colder, crueler, and lacking in sentimentality. While I enjoyed Okawa's version, I kind of prefer the rendition that Shiozawa created for us. At least that Iason seemed to have an ounce of human warmth to him. Can't really blame Okawa, though, as that's what I can tell the Iason of the novel is like.
Riki (Kentaro Ito) doesn't seem to me particularly exceptional or outlandishly bad either. He's okay. Miki Shinichiro really surprised me with his Katze. When I first found out about that being him in the preview, I was shocked that he could even sound like that. I mean...I heard him before in Escaflowne and a little bit in Weiss, but...geez, that was surprising. Raoul's voice is deeper than Iason's. That kind of bothers me...
Sound effects are improved upon. And the synth actually isn't that cheesy (I didn't like the music of the old OVA so much.)
I wish I knew more of what was going on. As it is...I just finished the first CD of Resonance, and pretty much Riki's done the deed with Mimea. Mimea, I prefer in the original, she sounds...I guess so breathy. Young too, but she's...how old are female pets usually? I recall in the novel that they said that males don't last as long as females, and I'm guessing they're usually kept around to breed, and that's that.
Oh, getting back to the whole novel thing--characterization. I can't stop comparing them to the anime. I know that's unfair, but the anime was the first thing I was exposed to back in the nineties, and I can't get over just how cold Iason is compared to the OVA's. You feel so much for Riki's plight, and it makes me want to smack Iason in the head for being such a bastard to him.
I could also comment at length on the ultraviolet purple prose of the (translation of the?) prose, but that's been done by people much better versed in the topic than I, so I won't.