I'm not sure I completely understand the Light Peak tech. Is it only for replacing slower I/O like DVI, SATA, USB, etc? Or did they have something in mind like external PCIe connectivity? A few fiber optic cables seems like good choice instead of a big bundle of cables for an external PCIe setup (if the tech ever makes it to market).

The tech will make it to the market...It might even do so in the case of HDMI 1.4+ where the need for 20 or so cables might be reduced to a single fiber optic cable...I know that they are now researching power over optical cable where power in the mA range are required...

Light Peak sounds rather like Firewire to me, but obviously faster and over a longer range. Firewire can do networking, audio, storage... basically the things that Light Peak is claiming. Firewire has the advantages of cheaper cabling and the fact that it can provide power too, and inherent advantage of metal cables.

However, a potential 10Gb/sec connection to a NAS would be quite cool, as would the possibility of one type of connection for external devices for a laptop. I can picture being able to have your primary video output (for mobile presentations etc) being turned into something to pipe data to an external video card once you have returned to your desk.

Light Peak coul be used for connecting devices like discrete graphics cards to the mainboard. Eliminating long PCIe connectors.
You would obviously have to have serial-to-parallel converters at both ends.