Bought a Lenovo X230 with a 6205 a few weeks ago. Wifi would not work for more than 5 minutes. It would keep showing limited access, but I could not use the internet. I tried all of the fixes, power settings, 15.xxx software. Finally I saw a bios revision for an ASUS router talking about fixing DNS dropout due to an Intel over-ping issues.
I bought an ASUS RT-N66U router to replace my D-LINK DIR-615 and have been using my WIFI for 1 week trouble free. Sucks to pay $170 to fix an Intel issue but at least my WIFI issue is over.