I have about 4k miles on my AT3s after switching from stock KO2s. Overall I like them better than the KO2s for everyday use although I think they have some downsides in performance driving. Like every tire, there are compromises and trade-offs but I would buy another set when the time comes and am happy thus far with my purchase.
Street: I think the AT3 looks great on the truck and much more aggressive than the KO2, also there's less of them around so you won't see many vehicles with the same tires (I always see Jeeps with KO2s). They are much quieter than worn KO2s which was a welcomed relief (my KO2s started HOWLING past 20k miles). I'm not with my truck so I can't take pictures, but yes, they are a good 1/2in - 1in taller than worn KO2s. For being 4lbs heavier, I didn't notice a difference in acceleration or stopping, I got mine in D load rating so the ride is marginally stiffer but still great. In the wet, they handle great, I found the KO2s really easy to overwhelm in rain with either too much throttle or quick steering, the AT3s hang on much better and trying to upset them in the rain is difficult. You mentioned gas mileage difference, I'm Stage 2 tuned but have noticed no fuel mileage difference.
Street tire: 9/10
Performance: Like I said, I think the AT3 is a bit more street oriented than the KO2 and doesn't perform as well at the limit. The biggest issue I have with these tires is what I can only describe as 'squirm'. I think it is a combination of the stiffer sidewall as well as slightly knobbier tires that makes the truck squirm on its tires when you start pushing it. I've had this feeling on both dirt roads as well as the street when you start driving at 8 tenths and can be a little unsettling initially. Compared to the KOs, the AT3s are not nearly as linear or smooth at the limits and exert a somewhat disjointed feeling when your ambition surpasses adhesion.
For low speed, the AT3s are great. I got the Rap up a jeep trail in Tahoe that I had no business getting up. The trail was full of football sized jagged rocks and the tires easily scampered up without any loss of traction and through loose rocks that I would anticipate the KO2s would spin a wheel trying to get up. The D rating also gives you a bit more peace of mind when dealing with these situations.
Performance: 7/10
