What will happen to my cake if I don't cream the butter enough?
The idea of creaming is definitely to incorporate some air into the fat-sugar mixture, which should give the final product a lighter texture. So perhaps your cake was a little heavier than it was supposed to be. Good creaming also helps distribute the fat well.

But maybe you managed to mix some more air in later in the recipe - certainly I imagine you could do better beating the batter with a stand mixer than I can by hand! And with a stand mixer I'm sure it was all mixed fine, too. So if the cakes weren't too heavy for you, it's not anything to worry about.