Does anyone see a need to support MIMO?
Mostly it is used in internal access points, there is an upcoming 802.11n standard.
But there might be advantages outdoors for P2P or P2MP links. One advantange (not in current cards, for future ones I think) is higher throughput, they are talking about 40MHz spectrum and using the guard bands between.
"pre N" Cards are already available - e.g.
I guess a comment would be helpful if anyone can see applications/need for this.