I installed the Mishimoto IC as I wanted to use the stock location. Overall, very impressed with the quality and fit. I haven't done any detailed testing, but watching IATs from my Accessport it seems to deliver good, consistent temp reduction compared to stock, with a quicker recovery after hard runs. And yes, I'm running the Cobb (Stage 1 93 octane) tune, which together is working great- truck runs better than stock in all conditions I've thrown at it. Also wanted to note I moved the front plate and my stock IC opening gets full airflow, which I think matters more than most people give it credit for.
And for what it's worth, I agree an IC is not really about adding performance in a non-tuned truck, but it will help maximize power delivery (existing maximum stock power capability) by not pulling timing due to rising IATs from a load, such as towing or extended full throttle runs. Power output at any given time is dependent on several variables, and keeping the intake charge cooler always help with power output.
Plus Mishimoto gave me this cool little stick-on penguin, logo-thingy for my window, so that alone was worth it.