I was briefly able to listen to the SRH440 today, though I'm sorry to say my exposure was very short and that I won't have the opportunity for quite some time to give them a thorough run through (some guff about Christmas gifts being reserved for Christmas). In that time, combined with the memory I have of the half an hour or so I spent with another pair last July, I can put together a rough assessment and comparison with the DT880.
First of all, I found the bass to be quite substantive, far more so than I remembered from the first time (and with greater punch and extension than the HeadRoom chart would suggest). This can only be a good thing, as my worry going into this was that the bass would be too light (ala the DT880). I would say it's not quite as well controlled as the DT880's bass, but that's a given from (a) a closed can, and (b) a sonic signature with less upper midrange presence than that of the DT880. It certainly isn't flabby or boomy, at least from what I heard, nor does it drown out the rest of the spectrum.
The treble is a little odd, though maybe this is just because I'm used to the DT880's strident lower treble. The SRH440 treble seems a little "sparkly" in comparison with the DT880, and though the former's treble spike might still be just a hair prominent for my taste, sibilance seems greatly reduced from the DT880. Overall, I'd say the treble is likely the weakest part of the spectrum in the SRH440, as it sounds as though it lacks a degree of coherence. It seems a little disembodied from the rest of the frequencies, though I really don't want to pass judgment here until I've had a long time to listen to them.
The midrange is wonderfully sumptuous, forward but not in a honky, upper midrange-driven way. If this is anything close to the Shure midrange that owners of Shure IEMs rave about, now I know what all the fuss is for. It's the part of the sound I miss most not being able to give these a go (why didn't I hide them when I left?!), and in the very few selections I was able to test I really enjoyed it. The DT880 has that typical "treble-colored" midrange that seems to come with bright-leaning, neutral cans. It has lots of upper midrange presence and an ultra clear but somewhat "dry" cast. I really like this sound, but I also like the SRH440's approach, and I find it subjectively more pleasing for mainstream music. I suspect it will be a lot less fatiguing than the DT880 here.
Overall, from my very short time with my new SRH440 (unamped, I might add), I find them competent, well-balanced, and very pleasant to listen to. I can't agree at all that they're markedly inferior to the DT880. They're different enough that they need to be judged on their own merit. It isn't fair to expect a closed can to ever sound as coherent, wide, or open as an open one, and the SRH440 does have a slight tendency (at least from what I heard) to sound just a little bit "canny." The soundstage is not as narrow as I've been on record as saying, and for this I owe SRH440 owners and Shure an apology. But it's nowhere near as wide as the DT880, nor does instrument separation seem quite as stark (again, not as much space to spread out--the Prestige Series Grados have this same problem to my ears).
For $100, I think I more than got my money's worth, but we'll see if anything awful crops up once I can give these some real quality time. For now, consider this a first impression.