Just updated to 16.10.0 from 16.6.0.
Before with 16.6.0, I always connected at 886.7Mbps and the "Connection type" in Windows Task Manager WiFi section showed "802.11ac" at all times.
Now with 16.10.0, connection varies from 650Mbps to 886Mbps. But even when it's on 866mbps, "Connection type" always shows "802.11n", it never shows "802.11ac" anymore.
Using 5GHz in both cases a few feet away from router.
Actual real-world speeds appear to be about the same but with more frequent dips in speed with 16.10.0.
Lenovo X220
Windows 8.1 x64 clean install + Windows updates
Intel 7260 AC Mini PCI-e card
Asus RT-AC66U 3.0.0.4.374.2050