Not surprising, and not necessarily for a "good" reason, the US Department of Transportation and the FAA have issued "an indefinite moratorium" on the upgrade to Microsoft's Vista OS , Internet Explorer version 7, and Microsoft Office 2007, according to an article from Information Week.
The moratorium was placed because there is apparently no compelling reason for upgrading and the upgrade is incompatible with certain software the organizations run.
Now, there's the rub. This isn't going to push people into moving to Linux or OS X or even running Firefox, as the technical problem appears to center around a series of applications that don't run well under Windows Vista, and don't run at all under those operating systems. So, don't get your hopes up for a migration to another OS anytime soon. Unless, of course, somebody in the government gets the idea that perhaps using the web as a platform makes more sense than locking in to any one vendor. Of course, some programs just aren't well suited to web-based implementations, so that may be part of the issue as well.