User blog comment:TheTobarMethod/Do AP's Need A QSS Upgrade?/@comment-3974211-20130904002950/@comment-5556439-20130904171845

I have honestly never agreed with investing in a expensive item due to a need to counterbuild IN LANE when your champion has a more important core item such as Tear or RoA on Karth/Kass. Reason? Most of the champions that Zhonyas can counter are very dive heavy like Zed, and can normally be dealt with in other ways rather than forcing you into a item.

Also I dont think you should use Zhonyas for anything other than defensive reasons as its wasted when used otherwise. Kind of like BKB in DOTA.