At time of this post now 13 hours until live order and download.
As to your ability to sync notes to your iPhone via Leopard, there are two things you need to know.
1- You can't, not directly.
2- You can, indirectly.
Now the grab at the top of this post, via Ars Technica's Infinite Loop blog, features David Chartier charting (hey its Friday and have been on road all week) a then-and-now couplet of grabs from Apple's MacOS X Leopard's 300+ New Features page.
On the right grab, seems the iPhone sync language seems to have flown the coop.
Sorry, syncing notes to your iPhone won't work either. Well, not entirely. The notes Mail.app keeps are actually just HTML email messages in a special folder, and if you use IMAP it will sync that special notes folder to your server. So in theory, if you have IMAP and you access your IMAP email through your iPhone or other device, you can view / edit those notes. But no, they don't sync to the notes your iPhone's native notes app keeps.
iPhone-using Leopard buyers: will you try this, or does it strike you as too much of a PITA?