Thunderbolt: External PCIe awesome, Cables Expensive
The external PCIe ports that Thunderbolt offers is really awesome.
http://netmgt.blogspot.com/search/label/Thunderbolt
Thunderbolt is kind of like the eSATA solution for hard drives, but is far more flexible (i.e. extending the systems PCI bus, not just extending a low-end SATA storage bus) - and people pay $$$ for it.
Technology like I/O expansion cages was previously only available on higher-end systems, mid-range servers, and mainframes. Now, external bus cages can be attached (i.e. ExpressCard), left behind on a desktop as if the person has a desktop unit, but just pop out the Thunderbolt cable on the laptop when ready to go home. Great for audio, video, performance studios, traveling performance studios, etc. This is really pretty interesting technology!
Thunderbolt is pretty clearly not aimed at least-common-denominator computing - external I/O card cages, heavy MIDI cabling, large numbers of monitors, etc. with the ability to have a portable form-factor are not the norm.
Cables are expensive though, that is a bummer... but bidding on eBay starts at $0.99 for budget minded! :-)