Use of the WBIs has ramped up considerably, to the point where I started driving on trips less than 500 miles. PIT has a single entry point for all airlines with about 7 lanes (plus the alternate, which you can't see when you enter the main terminal because it is up some stairs and on the other side). The scanners seem to be least likely to be used on everyone during rush hours (maybe 6am to 8am, I don't know about the evening). If used during rush hour a massive-looking line will build because the machines are so slow. Otherwise, it's a bit of a crapshoot (I never use the alternate as the person above suggested). Opting out is not much of a big deal there. I never had a problem when asking the TSO to pull his gloves from a box and change them in front of me.