I did not read all the forum posts yet but to my limited knowledge, a few Glock models are issued or authorized by US military units.
In 01/2012, I saw a few uniformed(ACUs) New York National Guard MPs wearing Glock 17 9mmNATO sidearms in SAS or drop leg holsters. The MPs were by New York City's Grand Central Terminal.
I also saw a TV program with a few LA National Guard MPs who used Glock pistols(17/19) while working the "road" in New Orleans.
The elite ACE(also called SFOD-D or "Delta") allows troops to pack the Glock 21 .45acp or a 1911a1 pistol. Some web weenies say Delta/ACE now uses the Glock 22 .40 but I think they mean the larger Glock 21 .45acp.
I'd read that a few USAF security forces(SF) carry the Glock 22/23 .40S&W on duty but that's unconfirmed by any USAF records or press releases.
Glocks are robust & well made but the standard M9/M9a1 & SIG's top rated M11 compact 9mmNATO will fill military holsters for many years.