I've had AT&T unlimited for a couple years and was able to convince Verizon to give me the $60 plan for unlimited talk/text + 2 gb data. Haven't cancelled AT&T yet, but I was on a road trip last week and lost AT&T service a bunch of times in the Georgia mountains, while Verizon never lost service.
Since I never use more than 500mb of data in a month, I'm probably going to switch to Verizon permanently. I'd save $30 per month and have better service. I'm hesitant to give up unlimited data, but with as little data as i use, it just doesn't make sense to keep it.