I will say this - Delta (and other airlines that I've seen) have gotten far more aggressive about deciding on a cut-off point where they say the plane is full and no more bags are going to fit on the carryon. The problem is, they also tell you not to check any valuable or medications. If I ever reach the point where they decide they're going to cut off before I get on the plane, I'm going to stand right in the middle of the entrance to the jetway taking everything out of my bag while everyone behind me waits so that Delta can check an empty bag - because quite frankly, in general, most of what's in my carryon qualifies as either medications or valuable items. My problem at that point is I have no idea how I'm going to carry all that loose gear onto the plane, where undoubtedly it'll be obvious that at least a third of the overhead bins are still empty because they've cut off bags too early. These days this nonsense of telling people there's no more room on the plane has nothing to do with there being no more room on the plane and everything to do with them trying to get the plane out on time.