I can't provide much more detail than that about the 1440 because I don't own them. This info I got from a close friend who owns all three Shure headphones and is more experienced than me (and has awesome gear). He said the 1440 sounds like an open version of the 940 without the rebellious treble. Sounds like a winner to me. In fact, he prefers it to the 940 and 1840.
IMO, the 1840 is a better headphone than the 940 overall. Open headphones usually provide better SQ. I also think the 1840 is a great value among flagships because I liked it better than my recabled T1s.
The 940, which is not too far off from the performance of the 1840, is an absolute bargain. It does have its flaws that keep it from truly competing with the best though (overactive treble, typical closed-headphone sound etc.)
One other thing that I think is worth mentioning. The HD800 is easily better than all of these. Sennheiser isn't stupid for pricing them the way they did. Compare all of these on a high-end setup and the difference becomes very clear.