High quality sound!
These replaced my old Sennheiser VC55s and the difference is amazing: sound is louder, clearer, bassier and more detailed at the same time. You can also notice the extra quality that an uncrompressed music file has (e.g Apple Lossless) compared to a compressed version, the downside being that i must now re-burn virtually all 3000 songs in my iTunes library to take advantage! Also, it is worth spending time getting them to fit correctly. Lastly, these may seem expensive but the sound quality really is worth paying the extra.