Just another data point. Mine (G80 3.8 AWD) seems to have a slight delayed upshift from 2-3 and 4-5. Only overtly noticable under light acceleration i.e. slowing down to take a corner around 20mph then accel.
I also notice it with ACC on in stop/go traffic.
Oddly I only notice it in standard drive mode, not eco or sport in similar driving style. Seems like the difference in programming might hide it in those modes.
Funny (depe nding on your perpective) is that I drove the car for a week prior to buying it and didn't notice it happening until after it signed the dotted line
I'm tempted to take it to my reputable transmission shop and have them diagnose it for me before I venture into dealer-land.