I purchased a new 2011 Journey SXT a few months ago with the Pentastar engine and I too have the transmission delay/pause problem when first getting the vehicle to move from a stopped state. It's like there is a hole in the acceleration curve for an instant and then it takes off. It's definitely the transmission though since if you put the gear shift into the manual mode and shift gears yourself, all is fine.
I haven't had the vehicle through REALLY cold weather yet so it should be interesting to see how that affects it.
I have already taken it into the dealership once re this problem, but their response was there is nothing wrong.