Fortunately, I tend to lag for months usually before updating major osx versions (I don't use my personal laptop much, and at work it's farther behind still), so didn't experience the wifi issue, but did with the cifs/smb change away from samba.
I haven't had connectivity issues, other than it takes a while to switch networks... At home, my macbook has about the best connections of any of my hardware, though my Nexus 6P may be better. I've been able to reliably copy files at 200Mbps+ over wifi. Worth noting I've got fewer than a dozen devices on wifi, and neighboring signals aren't that bad where I live.
At work, it's a bit noisier.