For me, between 70 and 100 hours they had a bit of a soft, ultra rich type of sound, a bit too mid-bassy, but at 120 hours (today) they have gained back the snap and precision in the mids and highs I like about them, and a bit of the low treble emphasis I didn't like. They still have overall a "thicker" sound than my Beyer 250-250's (which are fairly light and airy in comparison), and I can see why people feel the 280's don't really soundstage. They present images very close to you, nothing is very distant. But they do image, you can easily hear seperate images, just in a very close, intimate presentation. It might make some people feel a bit clausterphobic, but I like the envelopment. I'd still place them on par with the 250-250's for overall quality in absolute terms. But subjectively I prefer the specific (warm, intimate, weighty) type of sound the 280's have. It makes a nice contrast to the 600's, which are more airy and distant with a much larger soundstage.
I still have probably another 300 hours to go on them, at least, so we shall see what that low treble is doing at that point. Based on my experience w/my friend's 280's, it should have smoothed out by then. If not, a bit of cotton on top of the bluetak will probably be in order. We shall see. . .
(Edited twice to correct spelling).