I've been trying to get this NIC working for over a year now on my Samsung NP540; trying the various tweaks people list here and all the Intel drivers one after the other. After hours or days the drivers and fixes would always fail and the only lasting suggestion I read, which had any lasting effect, was to use the default Microsoft driver which came with Win8, although the throughput varied from 0 - 5Mb/s.
However, my laptop is all happy and working well now, having followed the advice of others here and removing the 6235-n and replacing it, in my case with a Killer 1202. Now I get 9 - 22Mb/s and it usually hovers around 15. Streaming and file copying is far smoother now. I wish I'd done this a year ago.
It's a shame to have to do this as my experience with Intel wired cards has been great and I prefer them over other cards, however this experience will make me hesitent to buy any device with Intel WiFi in future. Not because of the fault, any manufacturer can have a device which isn't up to their usual standards, however their continuing to sell it without resolution surprises me. Will happily keep using their wired cards though.