Why I do not upgrade Windows?

This is in relation to oldnewthing's windows upgrade post.

Personally, i do not upgrade on desktop because of third party applications. And the other reason is that, using automated installs, along with AD or SMS based software deployment makes it much simpler and less time consuming than any upgrade.

On the servers though, it is almost always paranoia, from 2K to 2K3 it was IIS settings, certified drivers from dell (in my case), recommendation from server manafacturers to upgrade firmware, drivers etc. ahead of time. Which almost always make the upgrade more complicated. AND most of all, it is easier to transfer settings/permissions/scripts than to fix them when an unexpected failure occurs.