Apple queitly released the iOS 6.0.2 update for the iPhone 5 and iPad Mini on December the 18th. TheThis 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 the update via iTunes or through an OTA update on your device.