Others say...

"Portability, Comfort, and Sound Quality for Cheap"
I am comparing these headphones to other products people may be interested in.

Shure SE110
Apple Ear Buds
Seinnheiser HD280s
Sony EX71
Skullcandy Ink'd

Pros:
More comfortable than ear buds or closed headsets
Extremely portable
Inexpensive
Excellent sound quality (recessed mids but excellent balance and richness for the most part)
Can hear the outside world

Cons:
Can hear the outside world, and they can hear you
Really need to be broken in for the sound quality to go from amazing to exquisite

On their own, the PX 100 headphones are extremely comfortable, fit well, collapse for portability, and sound amazing. They are relatively inexpensive and have a beautiful warm, boomy sound that was absolutely shocking when I first put them on. They are the best sounding headphones I have that I can wear comfortably.

These headphones have very similar sound quality to the HD280s but tend to make music more enjoyable. While the 280s are more analytical and balanced, the px 100s are more colorful and have more bass. They also do not highlight the highs so much that poor quality audio files are impossible to listen to. These headphones have half the impedance of the 280s which means you are getting richer sound in a more portable package for half the cost- with increased battery life on portables.

SE110s are slightly clearer and allow individual instrumentation to be heard better, but their sound quality does not create a balance (favoring the highs) that makes music enjoyable. They are also not comfortable. Both are good for classical music but I think the PX 100s are better because of their warm sound and deep lows, which really brings crescendos to a climactic finish where SE110s always leave the listener feeling cheated out of the final hit.

These have the same depth of bass response as the Sony 71s, but are more clear and are not as muddy in the mids and highs.

They are about as clear in the highs as apple ear buds (they are better than most people want to think) but also allow for clear bass and do not sound tinny and like someone pushed the right side of an equalizer to max.

The Ink'd ear buds are the closest in terms of overall sound to these and cost only a third of what the the PX 100s cost, but are less comfortable, do not stay in your ear, translate the sound of the cord, and only sometimes sound right (you have to have a perfect fit, which is nigh impossible)

These are my favorite pair and I only put them away when I *must* be isolated from my environment. They have an amazingly rich, warm sound which adequately plays any music I can throw at it. The clarity in the upper range with older music can lend to the bass overpowering some music. It isn't as noticeable as it is when my Klipsch 2.1 system plays the same song.

These are a no-brainer and I liked them more than the KSC75s, portapros, and bose triports I tried.

"Affordable and high quality, great for computer and iPod."
I'm extremely happy with the sound quality of these headphones (probably I wouldn't appreciate much better), and the price is fabulous. I use them with my laptop and iPod, listening to a variety of classical and popular music, and have found them excellent across the board.

As others have said, the fold-up procedure is a little cumbersome at first, but it's more than worth it to keep the headphones protected in the case when not being used.

"As good as the Bose Triports at a 1/4 the price!"
I bought these headphones about a year ago, and I love 'em. I needed a headset to replace my ipod earbuds---hated those. I did some research thinking I'd go Bose Tri-ports or JBL reference headphones. I stumbled on to Sennheizers at a Circuit City web site....I decided maybe $180 for Bose headphones at this time is not that good of an idea. I gambled on these and I 've never regretted it. The PX100's have excellent sound. Deep bass, great middles and great highs. These are also light enough to wear at work or while working out. I'm not the most gentle with 'em but they keep truckin'. When the time comes to replace these I will just get another set of PX100's!

"Good traditional type headphones for the gym"
I replaced a Philips set of in-ear headphones with these based on previous reviews and I'm happy with my choice. I like some Bass and these provide it (compared to the normal iPod buds for example). I find them easy to fold.

I have been using these while running on the treadmill for about 6 months now and they stay in place (the iPods fall out on me:-) ).

"Great headphones"
After buying an Ipod Nano, I wanted a pair of headphones that would sound great but easily fold up for portability. These headphones fit the bill.

Unfortunately for me, I can't wear ear buds or any kind of in-ear headphones as I find them uncomfortable and difficult to keep in place. At the same time, I didn't want bulky headphones that would be a pain to carry around. This purchase was the perfect answer!

The Sennheiser PX 100 sound crisp and clear and fold up easily, taking up little space when I travel. They're easy to work out in and carry around and the price I got was great. Buy them. You'll be glad you did!