What does Apple and Sun moving to x86 mean for Windows?

Now that the debate for the most part is over about the ability to run mission critical, consumer and business apps on x86 (some may have called it Wintel in the past which is a little unfair to AMD) is over, the industry has pretty much stated x86 is a viable platform for running mission critical applications and consumer applications (like video, animation, and other multimedia applications), the question is what does this mean for Windows?

Microsoft has had a tough up hill battle to fight moving into the enteprise space, especially the data center, for several reasons a lot has to do with the perception about the enterprise capability of x86 and Windows (a.ka Wintel) platform.  I think it will be important for Microsoft to attract mission critical customers and ISV's during the Vista/Longhorn time frame.  There is a difference between enteprise applications and mission critical applications, how many insurance companies bet their large back end policy and record keeping applications completely on Windows, how many manufacturing companies bet the plant operations on Windows, and how many hospitals, banks, and major hotel chains put there most mission critical apps on Windows?

I understand a lot of these applications are 30-40 year old (sometimes older), mainframe or other host based systems that just keep running and running, it is sometime very hard to build a compelling case to get companies to spend several million dollars to move.  However the ones who have moved off generally move very little if any functionality of from the host based systems to Unix or other big blue platforms, such as the 400.  The ones that are consider moving have CxO's not willing to place big bets on Windows because they do not wish to be the first in their industry to do so.

Now that Linux, Apple, Sun (and others) have validated the x86 platform as a enteprise player, Microsoft now needs to position itself to gain the trust of CxO's to win the mission critical applications.  Let's see what the Vista client and Longhorn server have to offer to mission critical customers.