First I'll say this was an amazing phone when i first got it, but after about 6 months the battery started draining alot quicker and and the phone lags now after leaving a program it takes a couple seconds sometimes for the home screen to come back up. i tried doing a reboot but its still does it. At least the phone does come with an app manager which im constantly using to close down programs after using them.
I love my Galaxy S4! I have had it for almost a year now and I couldn't be happier. I love the screen size, and how thin the phone is. My only complaint is that the battery does not last as long as I would like it to. I purchased an extra battery to solve this problem :)