Let's be honest here, Apple could only do it because of the relatively small size and loyalty of their user base. Apple users have proven themselves willing to

Let's be honest here, Apple could only do it because of the relatively small size and loyalty of their user base. Apple users have proven themselves willing to upgrade in a timely fashion. Windows users are more likely to stick with an old version if the new version gets bad press. Think WindowsME and Vista. If Microsoft were to make a complete, compatibility-breaking overhaul, they would have a lot of trouble selling it.