I liked how they sounded. They deliver a lot of bass without managing to overwhelm you with it, and they offer good detail without sounding brash. They remind a little of Velodyne's vPulse earphones, which cost less ($99.99), but aren't as comfortable as these Nocs.
Of course, with in-ear noise-isolating headphones like these, getting a tight seal is crucial to bass response. Walking around I was generally able to keep that tight seal, though I occasionally had to push the tips into my ear to retain a perfect fit. But as I said, I didn't have any complaints about their comfort level.
I'm fairly picky about what I use for day-to-day earphones, and I like the NS600s enough to make them part of my regular headphone rotation for my New York subway commute. While I'm not a huge fan of headphones that really push the bass (I listen to a wide range of music), it helps to have a little extra low-end when you're dealing with a lot of ambient noise like you are in the subway (low frequencies end up taking a hit). The NS600s strike the right balance and should satisfy bass lovers.
While the Noc NS600 Crush earphones aren't incredibly detailed, I found their overall sound profile very pleasant. My only gripe is that they're a little expensive at $149.99. If they'd been closer to $100, I would have awarded them 4 stars.