The result of all this work (with version 3.0 on its way too) is an OS that's so intuitive that many of us have never even felt the need to glance at the manual. The iPhone is just so easy to use that it almost feels instantly familiar the first time you pick it up. However, under that friendly exterior there are some hidden useful features that are not quite as obvious. In fact, we've managed to round up thirty of them. We'll cover the first fifteen in this instalment and bring you the final fifteen later in the week.