Although 802.11n has such revolutionary advantages, it still need to be certificated by the Wi-Fi Alliance.
As I know, the certificate procedure has already started since June 2007. The alliance declare that they would like to certificate it to meet with the 802.11n draft standards. There are 11 lab carrying out this procedure all over the world. And the sencond step is to meet the former 820.11(a/b/g) standards.
As there are two years since the standards was proposed, experts predict that the final standards will be finished at the end of 2007. While in fact, this regulation could not be utilized until the end of 2008 according to the situation. Many company started to use the 802.11n draft as the standards for their products, which aimed at occupy the profitable market 802.11n bring in. Of course this will also introduce some risk, and the vendor will have to modify their standards according to the final version published by Wi-Fi Alliance.
The picutre below is the sticker on the 802.11n products nowadays, we can clearly see that there is a draft signature beside the 802.11n to indicate that it is still in draft.