Using Gumi AI a bit lately (making a tech house sort of track). I'm liking the on-note controls for expression and pitch drift. Very intuitive. I'm probably going to end up playing with phoneme substitution a bit more and see how it works with AI, because Gumi has some odd pronunciations of English words. Not like typical "this word ended up completely" broken from conventional Vocaloid, but subtle things like "my" being said as "mah" or terminating plosive sounds lacking punch. The weird thing is they often sound right when you click the note but wrong during playback.