His acclimation wasn't great, unfortunately. PetSmart got a bad batch of bags (they were leaky). So their solution was to triple-bag the fish with extra water to allow for leakage. This left little room for air in the bag. Luckily, I live quite close to PetSmart so he didn't have to be in the bag for long. On the other hand, the leaky bags didn't allow for my usual float method of temperature equilibration.
I poured the fish, with the water, into a clean storage bowl. I then slowly (over an hour) removed his PetSmart water and replaced it with water from the QT. He freaked out every time I removed/added water during the process. As I didn't want to risk further stress on him, and the PetSmart water was either gone or incredibly dilute at that point, I poured him into the QT with the bowl water.
As for the QT, it was cycled and had housed several guppies just days earlier. I did an extensive clean after "transplanting" the guppies, as that tank was dirtier than I'd usually accept. This may have had an impact on the QT's cycle, but I'm compensating with SeaChem Stability (it can't hurt) and doing PWC.