This article provides a good overview of the product. The real selling feature of Sharepoint is tight integration with other Microsoft products. If you know Windows and Office, the learning curve is very low. In my experience, I've been disappointed with the product (sign in isn't direct and obvious, very little metadata support, very "boxy", no support for RSS, collaboration is basically just a threaded discussion, etc.)

Given the opportunity, I would move toward a product like Plone, Groove, Drupal, or Convea. Over the next several versions, Sharepoint will certainly improve...but it's currently a product that looks like a poor duplication of the more effective collaboration tools now available (both open source and proprietary). And even after the right product has been selected, the final quote in the article says it best: "That's the whole problem with collaboration: It sounds great, but getting people to use the tools is a real challenge".