There's some incorrect information in one of the posts above and I'll also attempt to clarify situations where balanced interconnects might be useful.
First, in a truly balanced circuit with XLR connectors, there is one common/shield pin, a positive pin, and a negative pin. In this setup the electrical audio signal is allowed to swing above and below common and undesired signals like hum and other common mode noise tend to cancel. It is true that balanced interconnects can be beneficial for long cable runs because long cables are prone to picking up more noise than short cables and balanced cables and circuits tend to cancel the effects of this common mode noise. But even with short cable runs, balanced interconnects may help to minimize the effects of ground loop induced hum or noise. In practical terms this basically means, if you hear a slight buzz or hum in your system, balanced interconnects may help to minimize or eliminate this noise. Other than being inherently quieter than unbalanced (RCA) interconnects, it is debatable whether there is any sonic benefit to using balanced (XLR) vs unbalanced (RCA) interconnects.
Microphonics are basically the effects of vibration on the equipment affecting the sound produced by the equipment. No interconnect will have an effect on this as the cables in your system do not contribute to or minimize microphonics.