Sizing up which Outlook version is right for you.
This is a question that has been raised to me recently a couple of times.
"Should we put in Exchange 2007 and stick with our existing Office 2003 install?"
Well, personally, No!
There is sufficient new functionality in Exchange 2007 that requires Outlook 2007 to work either fully or at all. Therefore, I suggest that you either go with Outlook 2007 or evaluate moving users to OWA.
Take a look at this comparison page here for more info:
Cheers
Nathan