Apple Logic Pro /LogicExpress Discussion

HI,
I'm starting to learn Logic Express 7.1 (on G4 800MHz). Previously I 
used Cubase VST, so I'm familiar with Antares AutoTune.... but the 
enhance pitch feature (Logic) doesn't seem to do anything! Does anyone 
have a clue about this, or does it work on other machines? Is there a 
plug-in called CORRECT pitch in the pro version, but only 'enhance' in 
the express version? I haven't yet (but am about to) install Apple's 
Pro app support update from late 2005 -- doubt this will help.

Any ideas about enhance pitch feature?

Mark H