The Arduino is absolutely cool, but the reason I recommend it is that it can be a good start to get introduced to <i>analog</i> electronics, that is even cooler for programmers. As after all the arduino itself for a programmer is just a small computer. Cool but nothing completely different especially if you used to write code in assember or C. But... analog programing, creating an AM receiver or transmitter, amplifying using a transistor, creating an oscillator, well, that is <i>magic</i>.