The real need in the future is not software compatibility, but instead data compatibility. The concepts of WinFS is not to lock Linux out, it's too aid in accessing data.
With drivespace increasing, it is becoming more of a task to just file data on a system. My standard users can't remember passwords, let alone remember where they filed their documents.
There is no reason my users should need to be computer savvy just to perform their day-to-day tasks. That is what makes computers inefficient. A computer is a machine designed to do a task or set of tasks. If a user has to create their own filing system for files and data, it is time wasted that could be spent assisting customers or making money.
With other technologies coupled with WinFS, a user doesn?t have to remember the filename, date, or even what program created it. They don?t have to assign keywords for searching or file it into special folder structures. The files will be searchable across all applications and uses. They were even developing a ?conversational? search capability in which the OS would recommend to you things related to what you are doing, just a person might bring up topics as you are speaking with them.
The simpler you make the use of the product the easier it is.

The real problem is that computers cost so much that people try to do everything with them. They load tons of software on it and expect it to work. A computer should be like an appliance that does what you need. Many software companies are doing this today. Look at AOL who wants to be your computer. The users who are not technically savvy think their computer is AOL. And really, that is the way it should be. My microwave may be able to fit 4 plates of food in it at once, but it won?t heat them up well at the same time. Just because a appliance can, doesn?t mean it should.
It should be the same for computers.

Along that line, I have over 2500 computers that I support. I engineered a precise image that does just what is needed. The users are locked from making modifications and it is built to run a limited number of applications. With that, the support calls have dropped by 80% in a 9 month period. The only problems that we get are hardware problems or users who are ?techs? and try to hack the computer to get around the lock down. The users who use the computer to do their work don?t have problems. I think Windows XP is solid when implemented correctly. I expect Longhorn to just be the same or better.