I have to admit, I’m a little confused.  Joel Spolsky – well-known in the software development blogger community – wrote a post in June of 2004 commenting on Microsoft’s dedication to backwards compatibility.  He cites the following story as an example of this dedication:

I first heard about this from one of the developers of the hit game SimCity, who told me that there was a critical bug in his application: it used memory right after freeing it, a major no-no that happened to work OK on DOS but would not work under Windows where memory that is freed is likely to be snatched up by another running application right away. The testers on the Windows team were going through various popular applications, testing them to make sure they worked OK, but SimCity kept crashing. They reported this to the Windows developers, who disassembled SimCity, stepped through it in a debugger, found the bug, and added special code that checked if SimCity was running, and if it did, ran the memory allocator in a special mode in which you could still use memory after freeing it.

Spolsky goes on to say that in the “Raymond Chen days” this was not unusual for Microsoft.  A quick search of Raymond Chen’s blog for the word “compatibility” confirms this – 66 posts containing the word at least once.  To really get a feel for the importance that Microsoft placed on supporting current customers, you need to read a few of these posts by Chen.
 
In Spolsky’s article, he praises Microsoft for their previous dedication to backwards compatibility, and then laments what he sees as Microsoft’s trend away from backwards compatibility…

Enter March 2006 – Vista is behind schedule.  The New York Times publishes the article “Windows Is So Slow, but Why?”  Their analysis?  Microsoft puts too much emphasis on backwards compatibility and not enough on new innovation. 

Eh?  So who’s right?  Spolsky or The New York Times?

The fact of the matter is that Microsoft is the market leader.  They have a “slight” majority of the market share, and with that majority they feel the need to help their customers make the jump to the next version.  They know – rightly so – that companies don’t have time to sit around and re-write applications that already work fine.  If companies won’t spend time to re-write, then the customers who require those applications can’t upgrade to the latest and greatest (Vista.)  If no one upgrades, Microsoft doesn’t get paid.  And being a business (a fairly successful one at that), Microsoft feels the need to insure some return on their investment – pretty simple.  In addition, they’re not going to start loosing customers any time soon.  The same companies that won’t do a slight re-write for the next version of Windows, surely not going to do a complete re-write to run their apps on a Unix, Linux, or Mac box.

Would it be nice to have Vista before Christmas?  Sure - I’m sure Dell would love it even more - but no one would buy the product when they realized that the applications they want to run no longer work.