I might be able to offer something here.
First, congratulations on the purchase. I wish they had used the name Allure here because it sounds more like Intrigue, but what the hell.
I've read some reviews where owners chimed in and some also said they didn't like the feel of the transmission. It is most likely a combination of the electronic chip in the transmission AND the electronic throttle control. There is an inherent delay in the sensors processing the inputs (including those of the potentiometer, at or near the gas pedal I presume). They mention that this is particularly annoying when accelerating from a stop on any kind of incline. I notice it on a hilly driveway.
Same thing here. The shifts when the pavement is flat, or in a slight decline away from a light, on a boulevard are almost not felt. Others are sharper. I chalk it up to the new mechanics since the Series III V6 came onto the scene. Like you said, none of the shifts are harsh and none of them feel as if there is anything wrong with the transmission. (I've always like the more consistent shifts of the 4T60 transaxle in my 92 Regal).
And good for you for not doing the flush. They like to sell that service item and I don't like to buy it. Also, if it makes you feel any better, Consumer Reports has given the Allure/LaCrosse's entire powertrain "full red dots" since its inception in 2005.
Sidebar/edit: about the potential headaches, did anyone impartial look at the car at the time of purchase, did the service advisor make any comments and was the fluid a very light pink without a burnt smell?