I am experiencing exactly the same issues, the only way to get the wifi back on is to completely switch the iPad off and then back on again, basically carry out a hard reset. This is very annoying, how many other people are experiencing this? I'm guessing this is a software issue as once the wifi is on and established it works fine. Have you a fix coming apple?
Guybrush-Threepwood and Paul-
Be sure the Settings - Airplane Mode is set to OFF.
Rebooting the CPU may solve the problem. However just turning the power off does not reset anything. To reboot, hold both the Sleep and Home buttons several seconds until the Apple logo appears. Ignore the "Slide to power off" arrow. After the iPad restarts, see if your WiFi has improved.
If rebooting does not help, or you have to repeat the process frequently, there could be a hardware problem with your iPad. The Apple Store Genius should be able to run more thorough diagnostics.
Can you use a static address at Starbucks?