Yeah my truck does seem happiest working too! I don't run the performance tune or even the mileage XS (even though it's great!) that often because of how much smoke it belches when I romp on it. I love it every once in awhile but not every time I kick it down on the freeway near the city... Have you downloaded the mileage XS tune from the website? It's great on fuel and super responsive. I wish they would release new tunes more often.
Tow perf does what I need it to, feels good, boogies and doesn't really smoke unless I really try to get it to.
I think the trans shifts well, I just want someone who has driven a few powerstrokes to let me know if it seems to shift right. I love the transgo kit it put in it, I did everything I could to it without dropping the trans. If it comes down, a fresh one is going up there.