Apple has just released iOS 6.0.2 for iPhone 5 and iPad mini. These are the only two devices to receive this updated at the present time. This update should help fix any Wi-Fi related issues you may have.
From the release notes:
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:
You can download this update through iTunes, or on your device via OTA update.