Similar story with my spousal units '09 Acadia. One of the rare times I was driving it the other week I said does it always miss and hesitate like this? "just when I drive it up hills." Oh, how long has it been doing this? "about a month, maybe longer I don't remember, but I kept forgetting to tell you and it seems like it is doing it now when I pull away from stop lights too"
I immediately thought transmission wave plate since that is a known headache with them. Good thing it is still under warranty...took it in and it turned out 4 of the 6 coils were bad. So they replaced 4 of the 6 coils and 4 of the 6 plugs under warranty (not sure why they didn't spring for the other two plugs or call us and ask if we would like to buy the extra two just so all are replaced at the same time at the present 68k miles). Better than a transmission, even better it was under warranty. I just hope the wave plate also goes kerput before the warranty runs out. This thing has not been very good, I try to buy american cars, but I am running out of options.