I had previously owned a pair of CX300's, CX400's (both Sennheiser) and a pair of mid-end Sony 'phones. I listen to a lot of music and tend to be a bit rough with earphones, so the cable on all 3 cables split revealing the wires. I considered upgrading to the CX500's, but decided to go with a pair of Shures as I had heard good things about them. Not wanting to pay more than £80 I opted for these.
I'm glad I did because the first thing I noticed was that the cable (and supplied extension) is nice and durable, probably the thickest I have seen on a pair of in-ear phones in this price range. While some may not like it, I prefer them to be durable as I have had them for over 3 months and they are still as good as new. They also reduce cable noise, a problem while walking/jogging or whatever you might get up to while listening to your music. The supplied foam buds (in 3 sizes) offer excellent sound isolation, far superior to the silicone ones provided by most manufacturers, and more comfortable at the same time. This allows you to enjoy your music at close to normal volumes (that you listen to in a quiet environment) without having to overpower the noise of the bus/traffic or whatever. Just make sure you look both ways when crossing the road ;) However, these buds are not as resilient as the silicone buds, and if you are not careful, pieces may break off of them. You may also need to clean them more often, as they tend to get quite dirty.
On the sound quality side, my initial impressions were that they provided quite a weak sound; not quite as punchy as I have been used to with the Sennheisers. However, once they had bedded in and I got used to the sound I found them to be far superior to any others I had used in the past. True, they do lack punch in the bass department, but I personally prefer a more bass heavy sound for most of the music I listen to, and I found I just had to fiddle with the equaliser settings on my player to get the sound I was after (feel sorry for iPod owners with no custom EQ). Instead, these provide a supremely clean sound at all frequencies, and are a world away from the Sennheisers and Sonys which tend to favour the lower frequencies and can seem overly bass heavy at times. They perform just as well with the thick, layered sound on hard rock tracks as they do on quieter acoustic tracks.
As said previously, to get the most out of these 'phones, they should be fed higher quality compressed material (not your standard 128kbps itunes affair), but 320kbps or uncompressed is a bit much for what these phones are capable of (most portable players don't support lossless codecs anyway). I'd say in the region of 192kbps to 256kbps is sufficient, depending on how important a factor file size is for you. There is lot said about people using heavily compressed audio formats, but the simple fact is, without professional equipment, at a cost of many times the price of these headphones, most people (not the professionally trained listener) simply cannot tell the difference between higher (or even lower) bitrate compressed music and music ripped using a lossless format such as FLAC or Ogg in a double blind listening test. Try it for yourself, I think you'll be surprised that the difference you hear is actually in your head rather than your ears.
Hmm, I think I said a bit more than I wanted to say here, so sorry for the essay ;)