If you think Beats are the greatest thing since sliced bread, my review probably isn't going to sway you enough to get you to buy these over the ever-popular Beats. But if you're willing to take the risk of being shunned by your friends, you will find your ears to be greatly rewarded.
I will start off by saying that you need a decent source of music. Playing 128Kbps music is going to sound terrible, but that's because it is terrible. You'll want 256Kbps minimum, 320Kbps is better, FLAC and ALAC is the optimum. You can hear poorly-done recordings and cheap files with these headphones, so don't waste your time buying expensive headphones and listen to junky files. Stick with $20 Walmart specials.
Next I'm going to say that blast these is just dumb. You're sticking speakers right over your ears and blasting at high volumes, which will damage the fragile structure of your ears and can lead to tinnitus. But if you want to spend the rest of your life listening to a whining/ringing noise, to the point where you can't fall asleep without background noises, then please blast away. It won't enhance the listening experience, only damage your ears and ruin your ability to hear fine differences in music. The plus side to that is that you can buy the worst headphones possible, because it'll all sound the same. Woo.
Now let me get off my high horse and get on the topic of the awesome headphones. The first thing that becomes apparent when you open these, is that Sennheiser really cared about the design. These don't look like shoddy plastic headphones which will crack and discolor. No, these have a slight retro look while using high quality components. It also comes with two cables, one for phone control and the other is a straight cable. Both are fairly long for mobile use.
Once you plug into the aforementioned quality music source, you will quickly discovered that these headphones have a very pronounced bass. It's quite boomy, but still tight and punchy enough that it won't be mistaken for a certain rapper's headphones. After around 15 hours of listening time, they become much punchier and the bass does not seem to dominate the listening experience. It is definitely these, but the mids and highs still sound great.
Speaking of mids and highs, you will quickly discover the benefit of buying high end headphones: that you can truly appreciate the music. Things that you take for granted in music, the instruments, are much easier to listen to and analyze. You have hear as the guitarist strums or plucks on the strings, as the drummer taps the cymbals or strikes the drums, as the bassists runs his fingers up and down the four strings. The music truly comes alive as you analyze the details, letting it wash over you, rather than letting a bunch of inarticulate noise be thrown into your ears. You can appreciate the dedication and talent of the artists.
While these are closed-back headphones, they are on-ear headphones. Very comfortable ones that use memory foam, at that. But what this ends up translating to, is that the are not going to block a lot of outside noise. And turning up the volume to block out outside noise isn't the solution, so if you're going to be in a loud place(aircraft, work place, driving), you may find that a set of noise-canceling headphones will suit you better.