The success began when the users of the social networking started commenting on their instagram and blogs about this new app. Then all their friends started using it, which became a chain effect.
The app became "App of the year" according to CNN (2012), because of it's design and creativity, with a excelent slogan "A new way to express yourself".
I think this app has every thing you could ask on a social networking, but we don't know how far it will go on popularity, and maybe it could just work for those with a big group of friends. Other wise, I do recommend this app for everyone who wants to get a new way to keep in touch with their peers.
I give 'Pheed' an 8 out of 10 for it's functionality and a 6 out of 10 for not being quite original at some point.
Here's another review that could help you to decide whether you like this app or not.