All I know is this, 4G = (EQUAL) SPEED. I want that, no matter where I am with my phone, to not have to solely rely on WI-FI connection for a quick browsing experience. I've used VZW 3G network and found myself wanting a faster experience. 4G will undoubtedly provide that.
IMHO, if this is not your primary concern, then there's no need for the Thunderbolt.
Would TB be worth waiting for if it was only capable of 3G speed?