never heard of being escorted to the front of the line because of a stroller. wheelchair or other disability, yes.
my experiences have been both on the west (LGA, EWR, JFK, MIA, IAD, BWI) and west coast (SFO, LAX) as well as in between - ORD and DEN. never once had this. on a Lufthansa stopover in FRA we were once escorted and allowed to "cut" the line, but I think it also had to do with a tight connection.
having a kid doesn't = special treatment.
most of the airports I mentioned above have premier/first class lines, and we always use those if available, but I cant say it makes much of a difference either way.
to the contrary, often in DEN, we are directed away from the "black" and "blue" lines (not that the color coding makes much of a difference) and told we must use the "green" line for first time travelers needing extra help or not familiar with TSA procedures, even when flying F.