The statement which has been issued on Apple's Web support pages says that while iTunes 7.0.2 may "work with Windows Vista on many typical PCs, Apple recommends, however, that customers wait to upgrade Windows until after the next release of iTunes which will be available in the next few weeks."
Some of the current compatibility issues between the current version (and previous) of iTunes and Vista include not being able to play iTunes Store purchases when upgrading from 2000 or XP to Vista, and problems with updating or restoring iPod software with iPod models.
One of the more serious issues however, is that "ejecting an iPod from the Windows System Tray using the "Safely Remove Hardware" feature may corrupt your iPod," Apple says. If you are using Vista, Apple recommends you always eject the iPod using the Eject iPod function from the Controls menu within iTunes.
Other possible issues Apple has highlighted include slow cover flow animation and contacts and calendars will not sync with the iPod.
If you own an iPod and are upgrading to Vista from XP or 2000, see here for further instructions from Apple on steps to follow to deal with these problems.