For months now, my Nexus 6 will not reliably connect to most wifi routers. If I reboot it, it almost always does for a short period of time (< 1 day). I suspect this happened with the last update to 7.0 in April, but not totally sure. Anyway I hope there is another update really soon as this is quite annoying.
More details .... it will 100% always connect to a very old Linksys router I have that is probably 10 years old. It has no password. I have 2 newer routers at home (one a linksys, one att), it will never connect to those. With the exception of right after a reboot. That scenario is the same with 4 different wifi routers at work.
To add to the irritation, the strength of cell signal has radically deteriorated over time, both at home and work. This thing is becoming a paper weight.