ST4:
Globalsecurity.org suggests that A10 squadrons in the theatre as of March 17, 2003 included the 190th FS (Idaho ANG), 172nd FS (Michigan ANG), 81st FS (regular USAF) and 75th FS (also regular). I have seen a google-cached news report from the Idaho Press-Tribune that states the aircraft were from the 190th, i.e. were ANG.
I have no personal knowledge of the exact differences in ANG, reserve and regular USAF training/readiness. One suspects that ANG pilots would not fly as much (i.e., not on a daily basis) as full-time USAF pilots, but that's only my assumption.