I've never had issues with non apple devices before. I did notice that I did not have 5ghz turned on so I did that changed the sp3 to connect over 5ghz and it went from ~2MB/s to ~9MB/s. At least that's usable.
I've swapped drivers and tried plugged in. Speed was exactly the same either driver, plugged/unplugged. About 1/8th the speed of my macbook pro, both sitting within 10' of an airport extreme. (802.11 N not C).