I am very impressed with Samsung Galaxy S4! It is super fast and I can switch between apps with so much ease its crazy! The design of the phone is perfect! The only negative thing I have come across so far is the weak signal that I get from time to time. I have had a couple of calls to drop but I do live in a rural area.
I have had many phones, including smart phones and I am mostly disappointed with this model. Within months I needed to replace it and Best Buy only replaced with a refurbished model, which has since gone bad, however they will not replace it again. The speakers are to quiet. The operating system us too allow. The screen set up is not very user friendly. My husband and son have the Samsung S5 and it seems to be a better set up. I am thinking about trying the S6 but am not sure if I want to risk being stuck again.