having accquired melodyne studio from someone who loves to lend stuff to me.. well, i can see why it doesn't get used.
i'm using cubase studio 4, and just.. UGH. if i have any tempo changes, it just adds a random amount of latency into any vocal parts after that (usually a couple of seconds). it's *incredibly* annoying. also, joey wont use it because it's not sample precise (you inevitably get 1-5ms latency at the end of a 4 minute track). that's not so much an issue for me, but yea, it's unstable, it's frustrating, and the interface isn't as intuitive as it should be.
i've yet to try rewiring it, instead of the plugin, which i think might help, but to be honest, the plugin should work.
if you want sx3, go with autotune, and use graph tune in it, or something.
i'm a protools noob, i can't say anything about it really.
thanks,