Hey all i thought this might help some of you guys out. So I just purchased my new Samsung Series 9 X4D A03CA - Canadian model
(15") and what worked for me quite by accident was when I did a clean install to get rid of the bloatware i re installed some of the programs i needed through SW update but didn't install the bluetooth driver, set the wifi adapter to maximum settings and I haven't had a single problem yet with downloads and streaming videos. I've kept the wifi running for at least 8 hours straight now, on battery and off, while repeatedly turning the wifi on and off to test how fast reconnects and there\s been no problems and it hasn't dropped out once. Also to note my Samsung came with the 15.5.0.42 driver which I have not upgraded, wireless N is also enabled working perfectly fine. Also tested on a G router and no problems as well. Hopefully this helps.
*previously bought and returned series 5 a week ago due to wifi issues (same card), tried eveyrthing, disabling bluetooth, wireless N, etc.
Seems like the driver model along with the bluetooth removed, not just disabled, seems to be working