Pros: Very good all-rounder, excellent value for the money
Cons: Tiny soundstage, can become uncomfortable after a while, mid-bass hump, leak a lot, not really suited for portable use.
These where my first good full-sized headphones and have served as my main headphones for home use since 2007 until recently (2013).
At $100 these are a good price, especially for people living outside of the US where Grados are just way too expensive. The sound is relatively flat, but the mid-bass is a little emphasized. Some might call that "fun" or "punchy", but I could live without it, honestly. The MS-1 sounds forward, mainly due to the small soundstage, but also because of a small rise of the upper midrange. These phones don't have that much extension on either side of the frequency spectrum. When listening to classical or jazz you really notice how small the soundstage is. With heavier stuff, like rock or metal, this isn't much of a problem. Surprisingly, these do quite well with organ music; the forwardness of these headphones really replicates the intensity of the instrument well.
The MS-1 are easy to drive and sound with almost any source or amp. They leak a lot of sound. I would never use them outdoors, you'd just annoy everyone around you! After a while they can become uncomfortable as well. I have to readjust them every once in a while, but eventually they just start to hurt my ears.
At $100 these are an excellent introduction to high-end headphones. They handle most music well and the fact that they don't need an amp to sound good is convenient, especially for newbies who are weary of spending more for a good amp. I still use them every now and then, even if my DT880 has now replaced them as my main headphone for at home listening.