Since Leopard's Mail.app keeps notes associated with a mailbox, if you associate your Notes to your Gmail IMAP account, the Notes folder will then show up in your Folders on the iPhone.
It's not Notes in the Notes.app, but it gets your Mail.app Notes onto the iPhone where they might be of some use.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20071105071359311