Unfortunately, I'd LOVE to comment on all of them, but I'm not allowed to. (One of the VAs, and a certain composer would shoot me if I did.)
So I'll try to say something without saying anything. The fact I'm commenting at all should say a lot. *cough*
... if I could marry a post, it just might be this one.
Have I mentioned how much I love you lately, Setsuna? (In a non-creepy way, of course, but still...)
Of course, I want to see Ryo performing the Jupiter songs myself, just because I think he should be happy being an idol FOR THE REASON HE JOINED INSTEAD OF PARADING AROUND AS A GIRL AGAINST HIS WISHES. *Ahem* Meanwhile, Len and Rin don't surprise me one bit. Of course, when Miku came out, I was half-expected Cineria, just to say a net idol vs. net idol showdown, but I knew it would never happen.
Not as excited about the Macross crossovers, though I'm not surprised. It's happened before; anyone else remember the Ranka Lee outfit for SP? Or Makoto's cover of Seikan Heikou or whatever that one song is? How they're going to explain it in-universe might be a bit tricky, though.
I need to actually get around to watching the anime to get excited about the girls from there, but still.
Also, there's five reserved vocaloid spots, or at least have the "voc" portion that Miku, Rin, and "Ren"(that really should be Len... >.<) have. My guesses: Luka (Most likely with Just Be Friends), Kaito (No clue for song), Meiko (Probably Nostalgic...), Gakupo (Again, not a clue. He's not really all that popular for solo songs.), and Gumi (I love all her songs so much, but I'll go ahead and guess Mozaik Role or Coward Montblanc.)