I'm happy so far, my truck looks like a truck!
Haven't been driving much lately, but it looks like I'm losing roughly 2-2.5 mpg in typical suburban driving. It could also be partially due to winter gas and warming up in the morning, but the weight difference (~20 lbs per tire) is a big factor. I did notice a difference in the amount of braking needed coming up to stop lights, but I've already adjusted to that. I'm hoping highway mileage will be about equal to the stock tires, but not holding my breath.
They've been great in the little snow we've been getting in the Denver area, no 4WD needed. One of the reasons I wanted the ATXs was that they seem to have more siping than a lot of the other AT/MTs out there. I'm hoping to get them off road soon, but I'm not sure when that's going to happen.
The difference in diameter is about 4%, so about 1.5-3 mph faster, depending on how fast you're going. (Just math, no actual testing) There is a bit of hum vs the stock tires. It's not loud or obnoxious, but it's there.