I was a frequent user for quite a while. It was never truly anonymous in that Yikyak obviously maintained some type of internal ID to identify you. This was fine with me. We had some deep, real conversations (along with the usual nonsense).
I stopped using it when they added mandatory profiles. For online discussion, there is a huge difference between anonymous and pseudonymous. While anonymous, no persona is formed in the mind of other users, except within the context of a specific discussion. It is impossible to form factions. Group think is somewhat minimized, because no one knows it is you that is not following the party line on issue A, even though you are totally on board for issue B.
When you are pseudonymous, factions form, grudges form, prejudices form. Suddenly someone remembers your position on gun control and assumes your position on the death penalty. If you say something stupid, it stays with you.
I don't want to share my sexual interests and my political point of views with strangers and have those things be linked to the same account (from the user perspective). I DO want to do that without that link. I think it tends to focus more on the issues, and let's people avoid the artificial barriers that otherwise might come between them.
When they made this switch, it was suddenly an entirely different app. It was no different than just finding a random web forum, except that you could be sure the people around you were geographically close to you (sort of). Completely non-anonymous Next Door is better in that regard anyway, and Yikyak no longer had anything to offer me.