I have a 4S and recently purchased a set of Sennheiser i300 earphones and found that the skip to next track button is somewhat erratic. It seems to start okay but after a few skipped tracks it becomes very hit and miss in registering the double click. I was planning to take them back for exchange but just realised that the standard Apple earbuds also have a switch which do the same skip to next track function. After trying those out, I found that they too start well but after a few clicks they are just as erratic as the Sennheiser. My question is, do people think the fault is with my iPhone or is this type of function unreliable in general? I have never used this function on any other device so I am not sure how reliable you are meant to be able to skip tracks. With both headphones I can skip up to 5 tracks before the skip function becomes unreliable. Thank you for any advice you can offer.