The HTC Thunderbolt has been quite a doozy for developers, we saw it take quite a while for the CyanogenMod team to get working data and unfortunately it seems all developers are facing the same issues. Getting the 3G / 4G LTE to work on custom ROM's has not been an easy task, but that hasn't stopped anyone from trying.
XDA forums member DroidVicious has been hard at work ironing out the kinks of his MIUI port for the HTC Thunderbolt, and the only thing non-functional at this point is the data, and SMS which he believes will resolve itself once the data is fixed. Sure, this does mean it is not yet ready for everyday use, but it is a step closer to more choices for Thunderbolt owners. If you are feeling brave, or have a few hours to spare that you don't need data connectivity, give it a shot!
Source: XDA; Thanks, Michael!