First, as there apparantly wasn't enough room for two complete voice tracks, they removed large portions of the JP dubbing (including some important stuff too, I think? Tal should know the details). The English track is similarly incomplete, meaning large segments of the game that were voiced in the original are unvoiced no matter what language you pick.
Specifically, the original JP track had about 10k lines, while the COMBINED TOTAL of the JP/US tracks on the US version has about 9k, that is, 4.5k or less than half of the original each. Things taken out also includes basically the entire ending and a bunch of late cosmosphere stuff.
Third, there's some sort of save-corrupting glitch that killed Snow's file permanently.
To be fair, I'm not sure this is a localization issue, and am partially convinced that it might be Snow's memory card. Gust games have always had weird save mechanics in general, and there's nothing NISA can do about that anyway.
Fourth, there's a game-freezing bug that forces you to beat a certain boss before the end of the third defense phase, whatever that means. Said boss is both required to complete the game *and* is fought 15 times in an aftergame sidequest with increasing difficulty each time, making that sidequest impossible to complete.
Think
Valkyrie Profile style battle system. Third defense phase would be the third time the enemy side attacks, so you get three turns before then (unless their speed stat is higher or something). It's not hard to kill the boss in three turns in the required fight (I could've done it in two if I unleashed my charged magic on turn 2 but I was going for overkill for lulz). The optional fights are doable by abusing an oversight in the battle mechanics, but that's too much of a pain and boring anyway.
Are all of NISA's recent localizations this bad?
They're... more just really halfassed. For Rhapsody DS they just yoinked the old Atlus translation and used it word for word, complete with grammatical errors. The extra content exclusive to the DS version was never translated because I guess they were just too lazy.
And really, as people have said, all of their releases in the last while have had grammatical errors all over the place. I assume they don't have a proofreader and in the case of Ar tonelico 2, they just had some third graders translate it (actually I think third graders would have done a better job grammatically at least).
Personally, I don't find these game ruining, but NISA has become really really lazy as of late. It's really frustrating because these are actually good games they're dealing with. I really wanted to see the extra content in Rhapsody DS... (Also, Cherie ranking hype!)