I have recently moved our domain from an Exchnage 2003 (Server 2003) to a new Exchange 2007 (Server 2008) setup.
All mailboxes have been moved. Most users are reporting that it says "Connected to Micorosoft Exchange" but also have a message saying "Folder lasted updated at xx:xx" which can be as much as two hours earlier.
All Outlook 2007 clients are up to date with patches and service packs.
2 users also keep having to repair their ost's with scanpst.exe and they are shutting down outlook correctly... I have tried recreating profiles on a few machines and that did not solve the problem. Accessing older messages in the inbox also seems to take much longer than more recent ones.