As Dan mentioned on his blog, those of you waiting to try out the final code (everyone currently using beta for sure!) can now download a 60-day trial of OneNote 2007 here. There is a full trial of Office 2007 Professional as well which of course is worht giving a spin too - and it shows off OneNote at its best with the full Outlook integration, blogging support through Word2007, etc. This trial version will last until after retail boxes are available in stores, and of course you can always convert the trial to a full version on-line.
For those of you not familiar with how the trial works, it is the *exact same code* as the final full release - not a lower functionality version. The difference with the full version is that the trial is set to "expire" after 60 days, meaning that the data in it becomes read-only at that point. You can remove the expiration at any time by activating it with a key that you buy over the net or in a store. So if you do decide to get the retail boxed version of OneNote in January or later, you don't have to uninstall and reinstall, just use the product key that came with the version you purchased.
You should *definitely* move to the trial if you are currently a beta user. The trial can read your beta or beta 2 tech refresh notes just fine. Uninstalling the beta and installing the trial will not cause any hiccup for you.
If you have Vista final release code, you need the trial (or MSDN full version) since beta versions of OneNote 2007 are not compatible with the final release of Vista.
The final version (in trial form or otherwise) has a number of fixes in it for stability, performance, search, and syncing of shared notebooks since b2tr, and of course hundreds of other fixes you may or may not have noticed in the beta.
Edit: if you have been running b2tr of OneNote or Office, bear in mind that final versions of any of these products cannot co-exist with b2tr versions of any of them. So the 2007 trial version of OneNote does not work with Office 2007 b2tr. 2007 trial version of OneNote cannot be installed when any fragment of b2tr is left installed, and that includes the b2tr version of the PDF add-in or the office file compatibility pack. Remove any and all trace of anything b2tr before installing the trial. There is a trial version of Office 2007 available at the same URL above so you can install that to replace b2tr - they expire at about the same time (the trial will last longer depending on when you start the 60-day clock by installing and running it) so you might as well run final code!