I haven't been familiar with it, but it looks like a great tool for certain types of production, voiceover, post, etc.
I don't know what its finesse level is, but having done a fair bit of hand editing of various types of raps and vocals, as well as other musical parts, I have to say that rhythm-oriented editing can be very tricky. (Now, aligning vocal parts might be a little better/easier since you would presumably use one part as the 'master' and 'slave' the others to it.)
All too often, in my experience, fixing the timing of one part can make the rest of the part seem wrong... you end up redoing every syllable/lick... and then the whole thing sounds wrong, stilted, awkward... wrong.
Particularly in rap, where idiosyncratic timing and hard-to-notate syncopation is so prevalent (at least in the most intersting performers), it's hard for me to imagine using something like this for lead parts. (But then, maybe that was never the point?)