The NASA Office of the Inspector General has a completed a review of the request for a waiver to use Customary units in the Constellation program. They do not support the waiver. The executive overview is here: http://www.spaceref.com/news/viewsr.html?pid=33782 (There is a link to the full report as a pdf at bottom of the page. There is QUITE a bit more detail in it)
The waiver is on hold anyway due to impending cancellation of the Constellation program. However, the report seems relatively critical of NASA's procedures for waivers and may spur some changes. In the appendix of the full report, there are some signs that USAF is the major service in DoD resistant to be fully metric, and that this contributes to NASA's problems in getting the aerospace industry to support metric.
