The Good News:
If you’ve got one of the Macs with the Intel Core Duo or any Mac Pro computers, then your Airport card has the ability to use the advanced 802.11n wireless capability.
The Bad News:
For some reason, Apple has decided to charge for the software to unlock this capability. Although the charge is minimal ($1.99), it is still annoying.
Note: You must have an 802.11n capable router to enjoy this capability.
Check it out: Apple’s 802.11n Enabler