Someone once said the best thing about standards is that there are so many to choose from. But what happens when there's no formal standard, and vendors want to develop products that are compatible with a "work in progress?" Can you claim compliance with a draft standard that's still in development?
Several WLAN vendors are doing just that, claiming compliance with the first draft of 802.11n wireless. Yes, it's possible to claim compliance with any specification, whether approved by a major standards body or not. To be fair, the IEEE does not specify interoperability criteria. This is one of the main reasons why the Wireless Internet Compatibility Alliance (WECA, now known as the Wi-Fi Alliance) was formed in the late 90s. The alliance defines interoperability testing criteria and provides certification (it invented the term Wi-Fi for interoperability) for products that meet these criteria.
For 802.11n compliance, the Wi-Fi Alliance says it will not take a position until the standard is done (at least mostly done). In the meantime, what are vendors doing to determine interoperability? This is another complex question, since the 802.11n draft will likely undergo significant changes before it's finalized (there were more than 12,000 comments received on the first draft alone). In addition, several required and optional features will exist in the final standard, again necessitating a group like the Wi-Fi Alliance to define what interoperability means.
Meanwhile, many vendors (including some whose products we tested) are working together on their own definition of interoperability. The real challenge will be to maintain interoperability up to and including software upgradeability to the final standard, which some vendors have noted as a goal in their marketing but obviously cannot guarantee.
We recommend looking at the current crop of Draft N products as just another incarnation of MIMO-based WLANs that offer higher performance. But we wouldn't count on upgradeability to the final 802.11n standard, a feature that is probably not all that important to residential users, the current target audience for most MIMO-based systems.