Well it was short-lived. I was north of Atlanta for a concert and on a whim turned on 4G. Much to my delight, every bar lit up - the very first time that has ever happened on my phone.
It also demonstrated to me the deficiencies of the speedtest.net app. The speakeasy website was reporting 9 to 10 mbps download speeds. The speedtest app maxed out at 3.5.
I don't actually plan to move to Alpharetta, though. Even full-on 4G ain't worth it to me.