Microsoft's Digital Image suite is no more. Due to the features of the product being available readily elsewhere, including many functions in Vista, Microsoft has decided to discontinue the suite immediately. It doesn't mean they'll be ditching it altogether, however. Retail supplies still existing and will still be sold until they are exhausted, and official support for it will remain for a tad under 3 more years.
Microsoft sheds very little details on the official page about why it was discontinued, aside from the features being available elsewhere. Perhaps development was too time or money consuming compared to other projects, or perhaps they do not want to compete with Adobe or other companies in that arena.