Linux Intel support is the best of all vendors, as far as I can tell. They have dedicated Linux driver devs and their specs are open. The quality of their drivers reflects this. In future I'll walk wide circles around anything broadcom.
Qualcomm Atheros also has dedicated devs for their Linux driver. Broadcomm stopped making wireless cards for the PC market earlier this year.
It looks like this may be a winner: AEX-QCA9880-NX
Except maybe they explicitly removed linux support:
http://www.spinics.net/lists/linux-wireless/msg110852.html
I can't find a hardware rev number on on the amazon page (was 1.0 ever sold to the public?). Also, the amazon page says it is for engineering samples only / contact vendor before ordering. Hmm.
According to Intel, installing Intel wifi adapters in computers or laptops "may be illegal":
https://communities.intel.com/thread/108092
I'll probably buy one anyway.
I have a 3x3 broadcom now, but it occasionally disassociates with the access point (and the box suffers from undiagnosed kernel hangs whether I plug an nvidia or amd video card into it...)