Probably one of the easiest upgrade routes in the system, same as when it was LGA-MDW. I have never missed an upgrade on this route, and the times that I have traveled with a companion they have always received the companion upgrade. Every time I have flown it there have always been empty seats in F, and yesterday afternoon there were only 3 of us in F. Once about 4 months ago I was the only passenger in F on a MDW-LGA flight.