I consider the ProComp AT to be an excellent tire, but probably about the most expensive ones you can find. For the first 10,000 they are the stickiest tires I have run in snow, wet roads and dry trail conditions including sand. From 10,000-15,000 miles they are okay. Around 18,000 or so they get very hard and are very good on dry road, okay in wet road and a nightmare in snow.
While I would not say don't buy them, if it were me I would plan to sell them at about 18,000 miles for what ever you can get for them. For what it's worth at 26,000 miles I'm showing about 7/32 per tire. They also seem pretty prone to cupping, but I'm not sure how much of that was from worn suspension components that were replaced about 15,000 miles into the life of the tires.
I would not hesitate to buy them again, but the price would have to be right and I would sell them at 15,000 miles or so. The reason for this is the new traction of the tires is simply awesome.