No need to be concerned about. Your notes will convert without a problem
to OneNote 2007 retail.
Microsoft will release at least one more beta version of OneNote 2007
before its release. It might be the case though that you need to upgrade
your notes to that one and then to the retail version. No one knows yet
though.
Microsoft is 100% committed to make sure there is a path to upgrade your
notes from B2 to retail, you will just have to make sure to follow their
instructions. This has worked perfectly for me from Beta 1 to Beta 1
Technical Refresh and from that one to Beta 2.
Keep in mind though, that OneNote 2007 is beta so you'll have to deal
with minor and major annoyances, crashes, potentially data loss (prob.
in conjunction with a crash), etc. Also, once you upgraded your notes to
2007, there is no way back to 2003. Hence if you are not committed to
purchasing the retail version, you'll be stuck once the OneNote beta
expires on February 1.
Patrick Schmid