Summary: I've had a series of Kilpsch Customs. I started with Custom 1's - great sounding but a little light on the bass. They didn't survive going through the washing machine when left in the pocket of my jeans though. Replaced with another set of 1's. These went AWOL (only to be found weeks later) and were replaced with a set of Custom 3's. Same comfort but more bass. The cable feels stiffer and frayed somewhat on mine but it in no way detracted from the sound.
Summary: I have to agree that these are not very easy to fit. I have come from Shure E2c, Shure E3c and UE pro.5s which were a lot easier to fit and keep fitted. However, once you get a good seal, the music quality is excellent. Just need to re-rip my collection now to a higher spec to get the most of these IEMs.
Pros: Sound quality Comfort once fitted Sound isolation
Cons: Initial fitting + further trial and error each time to get the proper seal.