Wi-Fi Assistant was originally a Google Fi feature that applies a VPN to open Wi-Fi access points - without user intervention. In fact, Wi-Fi Assistant is now (once you have the Play Services 9.6 update) capable of securing all open Wi-Fi, even ones where you manually connect. This is a huge move by Google that will hit the cellular carriers hard because if I'm able to use public Wi-Fi with confidence, and my phone is latching on to open Wi-Fi by itself - why do I need a large data plan?
This all takes Wi-Fi a step closer to being a viable alternative to cellular data, although there are still many issues. The problem is that managing a Closed SSID network is painful and complex, and Open SSID networks are subject to abuse. Wi-Fi also suffers from a handoff problem (i.e. it has no handoff method) and it's fairly easy to do a man-in-the-middle attack in coffeeshops - without 802.1X there's no way to know if that "xfinitywifi" hotspot is really Comcast or not. Wi-Fi Assistant solves that problem by providing a VPN back to Google's servers.
|zOMG so fast!|
For a while I'd been using an iPad in the evening because the screen was much better than my Droid Maxx. Now the iPad sits forgotten for days at a time, as I find the Nexus 6 screen good enough to handle almost anything.