Even though I've heard problems with Sharepoint scaling above a thousand users, which is related to Exchange's limitations. It certainly seems to be filling the low-end niche. Which is always Microsoft's target market on these things initially anyway. With Yukon and the like it's obviously going to get a boost into the larger scale enterprises.
"Microsoft Corp. said it sold more than 2 million end-user licenses for its SharePoint Portal Server last month, a dramatic rise in the number of seats purchased for the Web-based collaboration software. In the previous 12 months, according to Microsoft, it sold 5 million SharePoint licenses."
"Liberty deployed SharePoint PortalServer software two months ago as a knowledge management tool for its 125-person IT staff. "We actually needed it as a strategic base to our knowledge management system," Haroche said. "It's very easy to install. It's very easy to maintain.""