Don't see any reason to switch from google.
"You need a SharePoint server and license in order to collaborate, and either: You need to pay license fees for an on-premise version of Office 2010 or You need to pay an as-yet-unspecified subscription fee."
http://industry.bnet.com/technology/10002712/the-hidden-cost...
?
The Web Apps hosted on Microsoft's servers are free (or rather ad-supported). If you want to host them on your own servers, you need to buy various things. I thought Google Docs was the same way?
Sharepoint 3.0 was free to anyone with a Windows Server 2003 license. Once you build out that infrastructure a bit the marginal costs to upgrade into MOSS (SharePoint 2007/2010) start to look ok.
I personally prefer more socially focused solutions (e.g. Jive) but SharePoint is making huge strides as both a collaboration backbone and as a document management platform.
Some Fortune 500 companies are now building new intranet apps around SharePoint rather than standalone. There are a number of off the shelf solutions available as SharePoint "web parts".