Pros: Bass, nice Sennheiser logo
Cons: A bit less than average sound quality. Expensive.
I used these for a year for sports, and they are well made. They got wet couple of times, but still worked perfectly. I've since given them to my friend, who is still rockin em' after 2-3 years.
I compared them back in day to some 20$ creative IEM (probably EP-630? not sure), and I can quite confidently say that they shared the same driver with these. They had very slight differences in the treble, but otherwise same bloated sound. I couldn't tell which one was which in a blind test..
These IEM's got strong bass, and the overall sound is a bit muddy. Vocals are especially suffered. No soundstage to speak of. Midrange somewhat recessed. Highs not extremely detailed.