Results - Uplink
I expected no throughput improvement in the uplink direction and that's about what I got, with one exception. The new "Prep" location showed a 17% improvement with beamforming enabled. While that looks impressive, keep in mind that represents only a 4 Mbps average throughput gain in the test.
Beamforming Test Summary - Uplink
However, the IxChariot composite plot of the two tests shows steadier throughput with beamforming enabled as the primary reason for higher average throughput.
Test Location "Prep" comparison - uplink
The gallery below has all the comparison plots with beamforming enabled and disabled for all locations, uplink and downlink .
To my surprise, it looks like beamforming can provide a slight performance improvement. And even more surprising, it worked with two different vendors' products (although both are Broadcom-based).
My results, however, come nowhere near those NETGEAR touted in its announcement last year of its "Beamforming+" upgrades. I've marked up the announcement's plot with percentage calculations of the improvements NETGEAR showed it obtained with its beamforming implementation.
NETGEAR Beamforming throughput improvement - annotated
[Source: NETGEAR announcement]
I can agree with the 12% improvement—the most I obtained. But I wasn't able to obtain a stable link at low enough levels to obtain the 51% and 85% (!) improvements NETGEAR claims it can deliver. Note that NETGEAR's plot represents bi-directional throughput and that might account for some of the difference.
So I guess I'll have to circle around to this again in a few weeks once NETGEAR releases its new R7000 firmware.