Don't ask my how, but ... the "manual date set" method worked for me. For now....
My symptoms:
- No Wifi problems since 4.3 update. (Current build JWR66Y)
- Installed several games for my daughter two weekends ago to use up her promotional credit. NO problems. Also some dating apps for Daddy.

- Ran Scribblenauts Remix Monday or Tuesday morning. No kidding. It started after this.
- This Tuesday or Wednesday, I noted really slow download times. Then the wifi indicator went gray.[1]
- Indicator was BLUE when tethered to my Nexus 4 (T-mo). ?

- Throughput was spotty: sometimes Google accounts weren't synced, but synced fine manually.
- G+ and other content apps would sometimes connect, sometimes fail to login.
- Finally, last night, the stock E-mail client refused to connect to Yahoo (bad login or password), though I was using the correct values, and confirmed those on my Nexus 4.
- Setting the Wifi connection from DHCP to Static IP, no joy.
- Setting the router to issue a specific IP under DHCP, no joy.
- Confirmed these symptoms at two other locations with known good Wifi connectivity.
[1] Note that according to Google last year the blue indicator was based on positive connection to G+. Gray indicated some kind of local LAN connection, but no G+ connectivity. Access to other Internet sites was irrelevant.
My solution:
- Go Settings | Date and Time. Time was correct (NOT January 2000).
- Disabled "set time automatically from network."
- Set time to current time.
- Shut down.
- Rebooted.
- => Blue icon.
Testing now by installing all those dang games again (I uninstalled them Thursday, as logcat was showing Scribblenauts Remix making network calls on Wifi connection).