There you have it; good example of Software + Services … Microsoft Outlook is a locally installed software applications which, also according to this research the most flexible enterprise “SaaS” application.
The big distiction of Microsoft Exchange (Online) against the other Exchange “competitors” is the fact that Exchange offers choice in clients :
1. Microsoft Outlook
2. Windows MObile / iPhone / Nokia via ActiveSync
3. Outlook Web Access (Via Webbrowser)
… Cloud computing and software as a service (SaaS) has been getting some bad press lately. In an interview last month Richard Stallman said “If you use a proprietary program or somebody else's web server, you're defenceless. You're putty in the hands of whoever developed that software." This should be a concern for any enterprise considering SaaS. A SaaS provider can be just as proprietary as any software vendor.
In our recent enterprise SaaS e-mail report we addressed this concern and concluded Microsoft Outlook is the most flexible enterprise SaaS e-mail client available. The reason: Outlook can be used with three of the major SaaS e-mail services we expect to see in the very near future (Microsoft, Cisco/PostPath, and Zimbra/Yahoo). By supporting Outlook these vendors can provide a near seamless transition from on-premises to SaaS e-mail. Since there is no need to sell a new e-mail user interface the business case for making the switch is simpler. …
Source: Outlook, the most flexible enterprise SaaS e-mail client

