Differences between OWA (Exchange) 2007 SP1, Outlook 2007 and Outlook 2003
Firstly, sorry for not posting for a very long time!
Microsoft has posted up a neat feature comparison matrix for the differences between OWA, Outlook 2007, 2003 etc.
http://www.microsoft.com/exchange/evaluation/featurecomparison.mspx
We currently run Exchange 2007 without SP1. When SP1 is released near to Christmas we will be evaluating it then placing the update into production.