Recently finished my boxset, so I guess I can offer some thoughts:
-Most of the new cast members grew on me fairly quickly. I particularly like Uranus and Eudial's new voices.
-The only one I'm not sure about yet is Tomoe. His laugh is great, but the pitch is a lot higher than I expected. I do think it improved the more I watched though. He did do a deeper voice a couple of times, so he might handle the more sinister stuff well. I get the feeling that he'll use the deeper voice for his regular human self.
-I feel Cristina's Rei has improved a lot. She no longer sounds too deep for the part (like in season 1), or too adult. (like in season 2) As a result, her performance was a lot more enjoyable this time around. The rest of the returning cast is the same as always, so I doubt any opinions will be changing there.
-MOTD voices have gotten better. There's still some goofy voices, but there's more deep/sinister ones this time around.
-Waltz episode aside, the scripting was fairly standard Viz quality. Most of the notable changes have already been mentioned, but there were some new one I haven't seen mentioned yet. Tomoe saying his favorite exercise was stair-climbing was changed to rhythm gymnastics. Haruka's "I'm not letting you go home tonight" to Michiru at the end of 106 was changed to "Let's drive all night, just you and me." And as for Neo-Queen Serenity's letter? Instead of being written without kanji, Minako says " it looks like a child wrote it." Ami mentions her "participle is dangling", Artemis says "I think part of this is in Hebrew!" and Rei complains that ""daughter" is spelled with a q!".
And I think that covers it. But if there's any other scenes someone wants to know about, just let me know.