I like that about Milla. The VA does feel a bit inconsistent with her. It's not mannerisms that bug me, sometimes it just feels a bit flat, and Elize sort of feels like and adult trying to act like a kid and not doing that good of a job at it. But, it's fairly minor for me. VA's are no where near as bad (though amusing) as say Deus Ex (2000), and a lot of older games with VA's.
The shop system seems like it could be abusive especially if you explore, or grind heavily.
I really love this game despite me critiquing it heavily. Xillia 2 is supposed to be better, but then again I remember some importers being dissapointed in this one so I take their opinions with a grain of salt.