I do not like headphones that totally seal in my ears, as this does not do much for my eardrums. Normal in-ear headphones simply fall out so often. I have tried the type that clip over the ear, which are better, but with some energetic exercises these still fall off. I like the fact that they sit in the ear, without sealing it, so give better volume than the type that sit outside.
This new Sony design is great, easy to use, comfortable and it stays in place (it is even splash proof) and of course the sound quality is as you would expect SONY (they were first tried with my 8Gb Sony Walkman, but they also improved the quality from a Philips MP3 player). At this price I think these are great value and quality.