The dialogue does not work as well as KH1 ect. It's not bad but I think it's the weakest one of the voiced games.
Voices for KH1 and re:CoM are unmodified.
I hope they take the time to adjust the lipsynch for English.
Lipsynch can't fix what's fundamentally wrong with Re:CoM's english dub voice acting, and that is the fact that they were unable or unwilling to resynch lips to match proper voice acting so they had to do the reverse, synch their lines to the Japanese lip synching. This had the unfortunate result of some lines sounding stilted or coming off way too fast or too slow. Since they're not planning to redub the lines, even if they fix the lipsynch (no reason not too now, they're aren't working with FMV scenes anymore) the dub itself will still be rather low par.
KH1 and (hopefully, fingers crossed) Days won't have that problem.