I'm in the process of a 3 week migration of users from 2003 to 2010.
I've gone through a lot of the issues users have mentioned about free/busy 2010 and 2003 but not seeing what i'm seeing.
I have an admin account that when in outlook 2007 on exchange 2010 can see all users free/busy as well as the detail of the messages (probably because that user also has full mailbox rights)
If i use a normal user on outlook 2007 and ex 2010 this user can not see any free/busy information for users still on 2003 exchange. Just grayed out.
If i take the same admin user and use Entourage 2008 web services edition. that user gets a blank free/busy (essentially as if the user is completely open).
I've checked that public folder from 2003 is replicating to 2010 servers.. which i'm assuming is evident from the fact the admin user can see free/busy info and detail for the exchange 2003 users.
perhaps there is a global permissions thing I need to run on all 2003 users so that 2010 users can see free/busy?
note that 2003 users can see 2010 users' free/busy just fine.