Laguz are not in. Apparently they don't support completely unique classes like the Laguz or the Soldier/Halberdier (Nephenee is a Knight now ).

Also, there's a limit of 20 DLC characters at any time on your party (while there are over 120 characters just through SpotPass, and more through StreetPass and paid DLC, apparently [although some are duplicates, you can get Lyn with her paid DLC chapterrs, or as a SpotPass character in the FE Blazing Sword pack]). They are more than challenge map characters, as they show up on the world map and can be rerecruited if they fall (they'll eventually show up on the map again.

That's about as much as I can tell about it without playing the game.

Oh, and it's now officially gotten its NA title, which is new since the last time I looked it over. Fire Emblem Awakening.