Sfrounds: Biwring is very simple. At some point, the signal from your amp has to be split in order to feed the individual drivers in your speakers. Normally, this split occurs at the speaker terminals. With biwring, the split occurs at the amplifier terminals. Does it matter where this split occurs? Electrically, no. The full signal passes through both wires, and exactly the same signal reaches the low- and high-pass filters feeding your woofer and tweeter, respectively. Assuming you're using the same cable for both runs, any distortion introduced by the cable will be identical to the single-wire alternative.
In other words, biwiring makes no difference. However, many people report that they hear a difference when they biwire. There are two possible explanations for this. One is that listeners tend to be swayed by the power of suggestion. The other is that there is some mystical, magical force that no one's ever been able to identify, but some day a new Galileo will come along and tell us what it is.
There is one advantage to biwiring, however. If you're the type of audiophile who actively seeks out cables that color the sound, then biwiring gives you twice as many opportunities to do so.