Thanks, all, for feedback and suggestions.
I rebooted; no change. I deleted the network from N7, reentered pw key; no change. I installed Wireless Network Manager -- fixed networks, etc.; no change. The only thing different over the past week, before the 4.2.2 update: I added a network wifi extender. I simply unplugged it, reran a fix using the Wifi Manager app, and --
the wireless on the N7 is now more stable; it still drops occasionally but seems to reconnect on its own without my needing to manually deal with it. I'm going to reconnect the Wifi extender again, but with a unique SSID and see if that makes any difference. If not, I'll probably just return the extender. Too bad, too, because it's very cool.