To this day I have not heard a Compass pilot use their full call sign.
I did hear a CHQ 5xxx flight accept a clearance to descend that was meant for a SWA flight with similar numbers last night on Memphis Center.
The SWA crew said "If that was for SWA xxxx, somebody else took it". Controller said "I sure hope not", then about 30 seconds later "CHQ 5xxx verify FL350?" THREE calls lby Center later, the CHQ guy said "We'll go back up", then 15 seconds later "Confirm you want CHQ 5xxx back to 350?" The controller replied "I WANT YOU AT 3-5-0 NOW!!!"
About 5 minutes later, Chautauqua was handed off to the next sector, and the PNF acknowledged the call only with his numbers...but not his callsign.
This is not a bash on Chautauqua pilots; I know many who work for RAH and wanted to work there very badly myself at one point...but with as much stupid sh!t that goes on day-to-day (like *3* Cactus flights on the same Center freq that had numbers ending in xx26) we've all gotta be smart and safe out there...