You may already know this information, but I'll pass it along...
I am sucessfully (sort of) running Spambayes 1.1a2 with Outlook 2007 under Vista.
I had no problems running Spambayes 1.0.4 under Outlook 2003 and Vista (I did an inplace upgrade from XP to Vista - and subsequently did an inplace upgrade from Office 2003 to Office 2007).
Here is my current status... Running with UAC active -Outlook 2007 will crash on startup if the Spambayes addin is installed. Outlook will continue to crash until you give it permission to disable the Spambayes addin.
Once Outlook 2007 has started, I can go to the Trust Center, remove the Spambayes addin, then without leaving the Trust Center, add the Spambayes addin. Next I go under Help and enable the disabled Spambayes addin.
Spambayes runs great until I shut down Outlook and have to do the above all over again. I have tried de-activating Spambayes (as opposed to removing it) prior to shut down. This does not work. The addin must be disabled - however I am not aware of any user accessible tool within Outlook that would allow me to do this prior to closing Outlook.
If I use the 'Run as Administrator' option to start Outlook, Outlook starts normally with the Spambayes addin active. However, this creates other problems for me as one of the Outlook archive files is on a domain based network drive. Running as the Administrator for just this application does not allow me to log into this network drive when I am already logged into the drive with my own local machine account.
Right now, I shut down Outlook as seldom as possible and use Vista's sleep mode.