[quote user="ktegels" ]
   When everybody is running your stuff, you can't be as agile was you want.

This is a particularly interesting balancing act in windows:

In addition to new customers, a large segment of the market for longhorn are people who are running existing versions of our os, so we are essentially competing with ourselves in making longhorn compelling enough that these people want to upgrade. 
We must inovate significantly between versions, and offer a really compelling value add to customers for this to happen.

   However we also have to try to maintain backwards compatibilty with every application written for previous versions of the platform, including the ones that made use of undocumented stuff, or non-specified behaviour ( if they break, microsoft is blamed, whatever the reason... ).

It's an interesting line to walk...