I've got to start of by saying that it is a good quality well built product. There is no noticable difference between one or two headphones which make it ideal for sharing an ipod or portable media player which is the main use I get from it.
Gold plated plugs for great connectivity, meaning that no sound quality is lost through this device than just plugging your headphones directly into your ipod etc... Only negatives are that is it a little bulky which may not be ideal for everyone, but then again its not massive. The only other problem which might occur for others is that the connection socket is slightly tight on some brand of headphones but is no problem for the more expensive ones. Fantastic for the price, and the quality assurance that you associate with the "Belkin" brand.