Carried mine through security in the past month at:
CMH (Columbus, OH)
DET (Detroit, MI city)
MPS (Minneapolis, MN)
LAX (Los Angeles, CA)
SNA (Orange County, CA, aka John Wayne Intl.)
Got spot checked at CMH and LAX, they barely glanced at the GPS.
Also, in the pre-flight safety speech, Northwest Airlines explicity mentions GPSRs as disallowed items.