I started with the free version of this app which works pretty well except for the irritating ads which also burn thru your data allotment. The pay version works well enough; Ive tried several competitors, and mainly I used them as a night clock when traveling. Surprisingly, most hotels dont have illuminated clocks, so if you wake up early you would have to fumble for your iPhone to figure out the time. For that purpose, it is absolutely essential that the screen is easily dimmable (in a dark room the clock numbers are too much at full brightness), and this is one of the clocks which does allow you to dim the screen, although not with much precision. Also you can pretty easily increase the size of the numbers so that you can see it from across the room in the dark. It would be nice if this was a bit easier to resize, but at least it is doable, which is not the case with all of the competitors. Also, there is a bug in that once you dim the clock and then exit the app the brightness of the iPhone as whole is less than full. To solve this you have to go into the brightness setting and fiddle a bit; not difficult but it should be unnecessary.