Purchased 15 months ago here in the UK an SP4 Pro complete with keyboard plus pen. A month ago the pen ceased to function, the obvious choice clapped out battery. Getting AAAA ones from the computer outlet from where I purchased did not stock them, neither did any other shops I contacted. Amazon came to the rescue, though it to two weeks to arrive. checked batteries with a voltage meter, perfect. Fitting a battery did not help, the LED light never lit up and it was impossible to connect via Bluetooth. Contacting Microsoft they informed I needed a new one and could purchase at full price as it was 3 months out of guarantee. I asked if it could be repaired, the answer no, so I expressed the view was one expected to purchase a new pen every 15 months. To state that I am disgusted with M$, for their complete and utter disregard for a little over guarantee time after sale care when there is an obvious problem with the pen.