AirPort, WiFi, and 802.11
First, Apple's first AirPort base station and card were the final 802.11b. They were among the first, and cheapest, 802.11b products. (802.11 with no letters, is the same basic standard, only at a slower 2 Mbps.) I worked at Intel when 802.11b first came out, and our group (servers) decided to start playing with it (before Intel officially got into wireless networking.) So we had the choice between the $1000 Lucent WaveLAN access point (access point only, no router functions,) and the $299 Apple AirPort access point/router. It was a no-brainer. (Yes, it was ironic that the Lucent WaveLAN Silver card was about $199, when the AirPort Base Station was $299, and had a WaveLAN Silver card inside it, plus router functionality and a modem!)
It was AirPort Extreme that was 'draft g' compliant, upgraded to final g when it was finalized. (It helped that the draft went unchanged before finalization.)
802.11n, on the other hand, has different implementations by different vendors. (Much like the 56k modem wars between K56flex and X2, before V.90 was introduced.) So we may see that some hardware is compatible with the final spec, and other hardware that isn't. We won't know until the spec is made final, though, who wins. As such, Intel will likely not jump into the fray until a final spec is announced. (That is what delayed their .11g entry. While the last draft went unchanged to become the final spec, it was still only a 'draft' for about a year, during which time all other manufacturers had .11g gear, and Intel waited for it to be finalized.) But, as Apple isn't using Intel hardware for their wireless as it is, they won't have to wait.
The big advantage of .11n is, of course, transmission speeds. All 802.11 protocols are piss-poor. .11b's stated 11 Mbps rarely actually exceeded 4 Mbps. .11g's 54 Mbps rarely exceeds 20 Mbps. .11n not only increases the theoretical maximum to 500 Mbps, but it improves efficiency as well, allowing current 300 Mbps hardware to achieve 200 Mbps. It also significantly increases range. Both improvement are due to the 'MIMO' (Multiple In Multiple Out) antenna technology, which some manufacturers used on late .11g hardware to improve its efficiency. (While they claimed 108 or even 120 Mbps, they still would rarely even achieve the 54 Mbps that the standard .11g claimed.)
Then we come to the difference between the IEEE standard and the WiFi Alliance certification. The IEEE is an international governmental body that defines what is considered 'standard'. Nobody HAS to adhere to this (as long as they stay within government power/frequency requirements,) it's just meant to make it easy to produce inter-compatible equipment. That's why all .11g hardware works with each other, because they use the IEEE spec. But the '108 Mbps' .11g hardware isn't based on an IEEE spec. They meet the spec for 54 Mbps operation, anything faster is something that is manufacturer-specific. (When I say manufacturer, I mean the chip maker, not the actual router maker. Many router companies use chips from one or two chip makers, so routers and cards from different manufacturers can be 108 Mbps compatible, as long as they use chips made by the same company.)
The WiFi Alliance (WFA,) on the other hand, is an industry group that 'certifies' things as compatible, just for marketing purposes. ANYONE can make IEEE-compliant hardware, and call it '802.11g compliant'. Only when they pay money to the WFA to have it tested can they call it 'WiFi certified'. It's all marketing. And the hardware companies that control the WFA don't want to wait for the IEEE to finalize 802.11n, so they are getting the WFA to 'define' .11n so they can start calling their equipment 'WiFi n certified'. Even if it isn't IEEE compliant, they will be compatible as long as they bear that 'WiFi n' mark. (Just look out for 'pre-n' gear that says 'WiFi certified', that is only referring to the b/g certification. That means if you use equipment from a different company, you might only connect at .11g speeds.)
