Yes, for us with DD1, we transitioned to the sippy cup at the same time as we transitioned to cow's milk- about 1 year old.
She never really seemed to get the hang of the sippy until then, and didn't even express any interest in it all all until about 9 months. Personally, I think all the manufacturers who advertise their sippy cups for "6 month olds" are just trying to get you to buy them early.