Yes, i have had custom iem's for years however they don't work for everyone. In fact, they don't work for many, from the problem with fit and comfort to the problem of footfall noise due to resonance in bones or movement of the earpiece, or tissue inside ears that do not conform to iem's. For me it is the later because of surfing. It makes the tissue inside my ears less conforming so the iem isn't grabbed and moves very slightly. This creates loud noise when walking.
When voicing my problem originally, i couldn't find the reason, and i was contacted by an unexpectedly large number of head-fiers who had the same issues. I still use iem's in some situations and love them(JH13) but when i am going to be walking it is not worth it. For this reason i use over ears and on ears. Mostly those with issues using iem's try them once and swear due to expense wasted and then come back to regular headphones or just leave our community frustrated.
Either way, guess when the esw9 originally came out they were more of a novelty.