Router: ASUS RT-AC68U
Client: Dell XPS 15z notebook upgraded with 802.11ac mini-pci adapter (Intel Network 7260.HMWG), Windows 8.1, Intel 7260 driver from Intel website (19 Sept 2013).
The ASUS RT-AC68U has eliminated all the WiFi dead zones in my house (3 floors, 3600sf). I'm getting downloads around 100mbps in most rooms although sometimes as low as 6mbps at the edges. Within 10 feet of the router, I'm getting downloads around 280mbps. Wired Ethernet speeds are around 400mbps wired.
With a SSD attached to the USB 2.0 port of the router, I get file transfer speeds of 200mbps using USB 2.0.
With USB 3.0, I get around 280mbps speeds, and 400mbps wired. I had to disabled "Reducing USB 3.0 interference" to get USB 3.0 working.
I'm not sure if I really see the extra speed of USB 3.0 as throughput easily dips below USB 2.0 max speed when 10+ feet from router.
FWIW, I notice that the Intel Network 7260.HMWG seems to give me 25% better battery life than the OEM mini-pic WiFi adapter. YMMV.