After all the trouble they had with their Airport Extreme, ComputerWiz did exactly what any sane person would do with a computer they didn't understand, and took it apart. No? That's not what you would do? It's what I would do.
Anyway, the main goal was to find out if the new Airport's Gigabit speeds could have just been accomplished by upgrading the firmware of the old Airport Extreme, so CW ripped them both apart and took lots of pictures. All the watermarks make it a little hard to see, but what's clear is that the two different Airports use two different chips-- the earlier one uses the Broadcom BCM 5325, while the latest, Gigabit-speed Airport Extreme uses a BCM5395 chip.
What does this mean to you, as an Airport Extreme user? Not much. But it does mean that the Airport update is firmly hardware based-- you can't, for example, use an expander or a software update to speed up your old Airport Extreme unit. On the other hand, thanks to CW, you can get a look at the innards of both units, without having to take them apart yourself and that's always fun.