iTunes 9 is out! And working fine on my 10.5.6 mini 9 except for one thing - the iTunes store does not work unless you have Safari 4.03. Safari 4.03 is only available to 10.5.7 or above, so if you like me have stuck with 10.5.6 because of disk space concerns or similar, you won't be able to use the iTunes store if you upgrade, unless Apple do something their end to make it more backwards compatible.
Don't know if this affects you if you stick with iTunes 8, I might have to downgrade and see what happens.
Just a heads up :-)