I've liked Audio-Technica for a very long time. Used to own the AD1000, AD2000 and IM03, still have the IM04. When the LS400 was first released I immediately jumped on the bandwagon, mainly because I love my IM04 so much. Imagine my disappointment when I expect it to be an IM04 upgrade. The LS400, compared to IM04, is worse in almost everyway. Sound wise, the highs and lows are better on the LS400, but the cohesion is very far off--- it almost sounds like the drivers are handling different frequencies while in IM04, the transition between low, mids and highs is fantastic. The romantic mids is also gone, a radical departure from traditional Audio-Technica house sound. It sounds cold, uninviting, and too analytical. I even bothered to upgrade to both the 323A and 313 upgrade cable, and to my tremendous disappointment, they are just marginally better than stock cable. Fit wise, I don't see them as an improvement either. The IM04 can comfortably stay in my ears for a few hours, with LS400 I'm having constant ear pain in just minutes.
I suggest anyone who's interested in an 'Audio-Technica' Audio-Technica IEM to stray from this IEM. The tuning isn't traditional AT at all, and trust me, the fit isn't very good either. I regret throwing $600 on this IEM and $230 on the two cables. For the price I paid, these are absolute garbage with zero redeeming qualities. I still use them from time to time, and every time they make me wonder how I dropped almost a grand on this horrible garbage.