the pitch should be controlled in fractions of a half-tones, with a maximum 1 or 2 (or 3) semitones.
it has not to create weird effect.
it should be used to fine tune, for example, a slightly sharp note of a singer, or sax, or some other monophonic solo instrument.
the resulting sound should be natural and not "deformed" by this kind of processor.
i found flexor is useful for this kind or processing, and now i rely on it. but a standalone and standard device would be most useful...
for example:
http://www.planetz.com/forums/viewtopic ... highlight=