Well, with the first two episodes now over, I have some firm opinions on the casting.
Setsuna: Cautiously optimistic. Swaile didn't really copy Light, and there wasn't even a hint of Amuro or Quatre. He can play the quiet, reserved aspect of the character well enough, though the real test is to come once the role starts to demand more beyond that.
Lockon: I thought relative newcomer Alex Zahara did a fine job. He managed to capture Lockon's positive personality.
Alleujah: Some have doubts about this one, but I thought it was spot-on. Al is quiet and serious in the show, and that seems to carry on here. So what if it's like a subdued Inu-Yasha? It works.
Tieria: Cautiously optimistic. Not necessarily perfect but he often came off as distant, which suits Tieria. Sam Vincent is clearly capable of excellent expression in the role, such as with the "the world is being tested" line. This casting could really pay off later.
Saji Crossroad: The jury is out. I had a good first impression, but I'd like to hear more.
Louise Halevy: Kelly Sheridan nailed it. She sounded completely natural. Well done.
Kinue Crossroad: No complaints. Anna Cummer comes off as sufficiently mature.
Sumeragi: I thought Lisa Ann Beley was damn near perfect. Her delivery was excellent when Sumeragi was reflecting on Celestial Being's plan, much like Sam Vincent as Tieria. I'm now pretty confident that this was the correct casting choice.
Wang Liu Mei: This was perfect. Youthful, confident, smug, arrogant. Maryke Hendrikse fits the role like a glove.
Marina Ismail: Also perfect. I know, I'm a fan of the character, but seriously. I hope Paula Lindberg's acting is always that great. I'm now over Kelly Sheridan not getting the role.
Alejandro Corner: Jury is out. I want to hear how Andrew Kavadas sounRAB next week.
Christina Sierra: Yet again, a very appropriate voice for the character. I'm almost sorry now that Shannon Chan-Kent doesn't have a bigger role.
Feldt Grace: It's...acceptable. For now, I'm just thankful that Chantal Strand isn't making her sound like a young, starry-eyed kid like she did with Lacus in Gundam Seed. It's probably at least in part a benefit of her growing up since then.
Sergei: Cautiously optimistic. Not quite the gruff voice I imagined, but what Michael Dobson does works. Good, not great, it will do.
Patrick: He was an annoying, brash, arrogant loudmouth. In other worRAB, Trevor Devall did it right.
Graham: Cautiously optimistic. Overall, he sounded different and far better than he did in the trailer. People hoping for a "badass" voice may have been let down, I don't know. But Paul Dobson at least pulls off Graham's cunning intelligence, if not his aggressive zeal on the battlefield.
Billy: A little iffy at first, but then Kirby Morrow got good and stayed good by the time that Billy and Graham were carrying on long conversations. We'll see.
Second-stringers: All the random officers and politicians were actually...decent. I'm honestly surprised. In particular, whoever acted the Union President did it perfectly.