In a time frame of three of four months from now (fall 2009), I'll have to choose how to natively enable a handful of mac computers to access Exchange Server 2007 (email, contacts, calendar.)
Apple announced that the next version of Mac OS X 10.6, a.k.a. "Snow Leopard", will have built-in support for Exchange 2007:
Microsoft Exchange Support
Snow Leopard includes out-of-the-box support for Microsoft Exchange 2007 built into Mail, Address Book, and iCal. Mac OS X uses the Exchange Web Services protocol to provide access to Exchange Server 2007. Because Exchange is supported on your Mac and iPhone, you’ll be able to use them anywhere with full access to your email, contacts, and calendar.
Does somebody know if these new features could replace the Entourage client? Could there be there some limitations?