Based on a short playtime (well, watching Jennifer play - I will wait for the weekend trip to Scotland first):
Cecil: Not liking his voice so far. Apparently the voice actor Yuri Lowenthal voiced Seraph from Digital Devil Saga series (and the main protagonists in Nocturne), all of which I enjoyed. I hope for an improvement when he becomes a Paladin.
Kain: So far the best with a gruff and dark voice that matches the new Batman look. According to the ever unreliable Wikipedia, Liam O'Brien is "usually cast in some of the most unusual roles, as such he tends to play characters that show signs of insanity or are complete evil geniuses".
Rosa: An elegant voice, though a bit too Americanised for the setting. I rather enjoyed Karen Strassman's performance in Odin Sphere as the Valkyrie Gwendolyn, but for some reason it isn't right here.
(Young) Rydia: No idea who the voice actress is, but nothing wrong with it. She sounds like a naive kid, which is exactly what she is when she first joins the party. We will see if her voice changes as she matures.
The new translation is an improvement over Final Fantasy IV Advance and the other English versions. The language has been spruced and cleaned up too. You will be glad to know that touch screen controls is optional and you can stick with superior face button controls. I will write more once I get a chance to play it this weekend and get the hang of it.
Oh and Namingway is now called Mappingway but changed his name to Livingway at Kaipo...
You can order the North American version of Final Fantasy IV DS here.