Apple has released iOS 6.0.2, a minor update that looks like it fixes some Wi-Fi problems that users are reporting. The official description is pretty vague:
iOS 6.0.2 Software Update
This update contains improvements and bug fixes, including:
• Fixes a bug that could impact Wi-Fi
For information on the security content of this update, please visit this website:
Get it via the usual locations, and hopefully it should stop any further problems you might have connecting to a Wi-Fi network.