MS Outlook main window will not open. This problem continues from Developer Beta 3. Outlook will not create a new identity and no other hints found on how to rectify this problem. So ... back to Mavericks.
Outlook 2011 works for me. Rename your Microsoft User Data folder by putting XXXs in the name.
Open the Database Utility and create a new Identity.
This should open Outlook in a new blank Identity in a new Microsoft User Data folder in Documents.
If this fails, test in a new User. If it works in the new User the problem is not with Yosemite but your User's folder.
I had trouble with my default Identity but since I only had IMAP accounts I was able to enter accounts a let it all download from the server. Other accounts worked as expected.
Entourage 2008 worked with all my Identities.