Excerpt from an Office/SharePoint 2010 update overview
As you look across the spectrum of capability for Office and SharePoint 2010, you'll see that there is a tremendous amount of capability for developers building solutions. Office is frequently used as the front end to line of business processes and applications. And let's face it, if you're an information worker in an enterprise environments, and you are asked to use several of the 50 (on average) line of business systems present in an enterprise, it makes A LOT of sense to surface those things in Office. For end users, Office is an environment that is familiar. For Developers, Office is a way to accelerate the end user learning curve by a substantial amount. Multiplying that across the number of users in and systems / processes in play, the math points to giant savings for business applications.