I did read the reviews prior to purchasing these - I also already own Sennheiser head-phones and ear-buds so know what sound quality to expect. I'm afraid I have to say, that I was disappointed.
On a positive note, once the shape has been made to fit they never come off. The remote works flawlessly with the iPhone4. They are very light. They look great. When you push the speaker hard onto the ear canal, they sound great. However, that last point is the just problem... for me, they don't fit well enough to sit over the ear-canal properly and provide that fuller rich sound I'm used to from Sennheiser - sounding more like a £5 pair. Also, I found that they hurt after a while too.
I've come to the conclusion that it's a gamble buying hang-on earphones like these, because everyone has different sized and shaped ears. I've no doubt some people will love them and whilst it comes with different sized covers/pads to help, there is no one-fits-all product. I've returned mine and will try some which are still sports/hang-on ones, but ear-buds which go inside the ear canal instead.