I need help with my new 24-70 f2.8

Hello all,

I finally I was able to save up money for my weekend photography shoots to get into the FX world. I did pull the trigger on D600 and a Nikon 24-70 f2.8, I am reading online about the zoom issue with the 24-70 f2.8 and I am scaring my self right now and I am imagining that I might have this issue, so please if someone has the same lens  can confirm the following:

-  My zoom ring does not grind or click at all but it is stiffer that the focus ring, is this normal?

- I have a Sigma 70-200 f2.8 and the zoom ring there is also smoother than my Nikon 24-70f2.8.

- it gets less smoother from 50 to 70 than 24 to 50. again I do not hear any clicks or grinds.

I am concerned because it did not feel as smooth as the focus ring or my zoom ring on the sigma.

I do not have any local stores that have this lens on display so I can go and try them, I bought it from Amazon and I still can exchange it but I do not want to do this if I am just imagining this issue.

Thanks,