I'm starting to see blips of LTE in southern Wisconsin. I caught my phone going to 4G on Milton Ave. in Janesville yesterday. It stayed up as long as I was on Milton, but once headed out of town it dropped back to 3G. I live fairly close to Milton, but I couldn't get the phone to reconnect to LTE later on.
Around Oregon I saw it flip over to 4G again, but about a minute later would fall back to 3G. If I switched mobile data off, then on again, it'd reconnect to LTE, then fall back after a couple minutes.