I blundered across an interesting article in Antenna Systems and Technology magazine (Nov/Dec 2005, and yes, I'm behind on my magazine pile reading).
Why MIMO Matters
formatting link
compares the performance of Linksys (Airgo) SRX MIMO WRT54GX and WPC54GX verus Netgear RangeMax beam switching (Video54) WPN824 and WPN511. Unfortunately, there's no comparison with a beam forming product.
It's quite an interesting read and method of testing (using a laptop on a turntable). One item that caught my attention was that the Linksys combination allegedly still ran at 5Mbits/sec thruput, going a distance of 206.5ft, through *FIVE* walls (ceiling and floors). I don't believe it, but it may be possible.
Some related stuff by the same author/company at:
formatting link
Video54:
formatting link
formatting link