Just to share my opinion. Ive moved from senny PX100-II to m1s, without any experience with IEMs. When they arrived, I didnt like the small amount of bass and more highs to be heard, but after 2 days of listening to, i must say ive fallen in love with them. Im not kind of the biggest audiophile, but i can hear some differences. Im listening to huge spectrum of music, from jazz, downtempo and DnB with dubstep all way to many kinds of new and also old metal. As they are supposed to sound balanced, I expected them to be alright when it comes to metal, but weak (due to lack of bass) when it comes to bassy electric styles, like dubstep is. In fact, i was shocked, after some burning in by regular usage (i have them almost a year now i believe), how great they represent each style. Ive got really very fast used to their balanced sound, and I no longer lack any bass or anything. When my friend borrows me his porta pros, im sick from all those basses and everything else behind. There is really a large, LARGE gap between the quality of those 2. The clarity of m1 compared to bassy and non-detailed portas, just keeps me stunned, because there is almost no price difference. Also, it pairs very well with my iTouch, so I can just recommend m1s to everyone who is looking for some balanced IEMs, and also to everyone who is new to IEM (because they are not so expensive). I would never throw them away.
Oh and yes, so i dont forget, the cable is really cool, it never really entangles, so i just pull them out of my pocket and they are instantly ready, great feature.