I've had the m6 for quite some time now but threw them on the bookshelf after first impressions. I have the microphone version (m6p) and there was a problem with the mic line bleeding into the audio line. I had to open the mic housing and place an insert between wires so they wouldn't touch. The housing broken so its held in place with electrical tape now. It was a horrible first impression to the m6.
At first impression, I thought the highs were going to make my ears bleed. I should note that I like to listen to my music fairly loud. I have a 5th gen ipod video and mostly listen to electronic, hiphop, rnb, with a side of acoustic and indie. The bass was fantastically tight, the mids seemed somewhat recessed, but the highs were shrill.
After a year, I decided to give it another try. After burning in for >100hrs, the sound definitely seemed more balanced but something still didn't feel right.
I replaced the tips easily with sony hybrid tips and what a difference! The highs were perfect, the bass was still tight and mids seemed more controlled. They are 10x more comfortable and i don't have to constantly play with them in my ear to get a good fit. I've tried shure foams tips but I believe foam tips are a pain to use for an on-the-go use.
so for anyone who reads these, USE DIFFERENT TIPS if you're not getting a good fit.