Very disapointing. I bought a pair of these and the first thing I noticed when using them was the background hissing noise. Something I've since found out seems to be a common problem with cordless headphones.
I couldn't put up with the hissing so I got a refund and bought a set of corded headphones instead. Half the price and much better sound quality.
It seems if you want a decent set of cordless headphones you have to spend £100 plus. If you've got only got £20-£40 to spend then avoid cordless, and just get yourself a decent set of corded headphones.