I’m still running iOS 7 Beta 3 on my iPhone 5 and iPad mini and I’m still having issues with WiFi connectivity and some faster-than-usual battery drain. The WiFi issues don’t have much rhyme or reason — I have really good WiFi signal at home and recently boosted it with an Apple Airport Express — and connectivity is still a problem. Both my iPhone 5 and iPad mini will drop my WiFi connection, then reconnect.
I’ve done some research online, and if you are having similar WiFi and battery issues while running iOS 7 Beta 3, a possible solution is to make a backup of your data first, then do a complete fresh install, then restore your backup onto your device. This may be a possible solution. Or, hopefully we will see improvements in subsequent beta releases. Time will tell!