I've noticed mine drop from indicating 4g LTE to "4g", and it dropped to Edge once. It seems to prefer LTE tho, and quickly reconnects to the LTE signal. I've hit no dead zones, including leaving my home wifi.
Big numbers! It took about 2 seconds to upload this screen shot:
http://i119.photobucket.com/albums/o149/loaded321/Screenshot_2012-11-19-11-45-02.png