I don't have the Tokina, rather the Nikon 12-24. However, I am about to swear off polarizers on this lens due to the issues with the sky. It also occurs (and can be even worse) when capturing scenes with the intersection of water and sky. I spend way too much time in post processing trying to clean this up.If you are doing a lot of outdoor/landscape photography, I'd certainly recommend a polarizer. It will remove the cool sky-blue reflections from foliage, water etc giving you much richer colors. Take care when photographing the sky at the wide end of the zoom as you may get very uneven polarization (the maximum effect is in a band 90 degrees from the sun).