I guess I am replying to a very old post now...
I have a 2013 Eco with AT, 42K miles... I find that the shift from 3rd to 4th is very weird, for lack of a better word. Every other shift is nice and sometimes barely noticeable. But from 3rd to 4th it feels like it is lagging and it takes longer than every other shift. This does not happen when the temperatures are colder, as in 60F or colder. But once the temperature is 70F and hotter, and the engine is warmed up, that gear change is not nice.
I just had the fluid changed in hopes that it would make a difference. Not sure yet if it has.
Ugh, what I really wanted was a manual but there weren't ANY available within 300 miles when I bought my Cruze.