Oh, by the way, I forgot about a setting I found that did improve my Wifi behavior. I think, ultimately, that my router is the flaky component (I have an 802.11ac adapter on my desktop that doesn't always work well either). But, here's what I did:
Dialpad, *#0011# . When you hit the last # a service mode screen automatically appears.
Hit the menu button, then pick Wifi.
On the next screen you'll see a bunch of settings printed, and one big button under "WIFI Power Save Mode". Tap that button to make it say "OFF". Back button your way out. Reboot the phone, then go back into *#0011# -> Wifi to verify that Wifi power save is still off (a bug in earlier Samsung versions defaults this to "on").
Mine is still flaky, but much improved. I am using a bleeding edge protocol, though.