In a memo entitled, “Dawn of a New Day,” Microsoft visionary and exiting software chief Ray Ozzie urges the Redmond giant to envision a “post-PC world” and criticizes Microsoft for not fully realizing the opportunities he highlighted in a 2005 ‘Internet Services Disruption’ memo.

“Yet, for all our great progress,” writes Ozzie in his latest memo to executive staff, “some of the opportunities I laid out in my memo five years ago remain elusive and are yet to be realized.”

Earlier this month, Ozzie joined a long list of executives who have recently stepped down from high-level positions at Microsoft. Ozzie, who had replaced Bill Gates as chief software architect, was best known for spearheading the development of Lotus Notes. In 2006, he became chief software architect after Gates left the position, and oversaw the company’s cloud computing initiatives, including the Azure platform and Internet services.

According to the Wall Street Journal, the news of Ozzie’s departure spread in an e-mail sent to Microsoft employees from chief executive Steve Ballmer. Ballmer wrote that Ozzie will focus on the Redmond giant’s investments in the field of entertainment during a transition period and leave the company in the coming months.

Now Ozzie is asking Microsoft to step up its game as the company belatedly rolls out a new line of smartphones in an already crowded and highly saturated wireless devices market.

"Let's mark this five-year milestone by once again fearlessly embracing that which is technologically inevitable," Ozzie wrote. "The next five years will bring about yet another inflection point -- a transformation that will once again yield unprecedented opportunities for our company and our industry catalyzed by the huge and inevitable shift in apps and infrastructure that's truly now just begun."

One of the key changes Ozzie calls for is greater product simplicity: “Complexity sucks the life out of users, developers and IT. Complexity makes products difficult to plan, build, test and use.  Complexity introduces security challenges. Complexity causes administrator frustration.”