Samsung phones have one major failing -- you can't use them hands free in a car UNLESS you have a rock-solid internet connection because voice commands require interpretation by an online service. Even when it works, the interpretation accuracy is pathetic compared to my old Blackberry Torch, and the lag time for response is frustrating.
I'm running a Galaxy S4 phone for the last year and a half, and I love it. I will definitely get another Samsung phone when its time for an upgrade.
I recently got a Galaxy TabS 8.4 tablet as a birthday present to myself. I really love the power-saving modes, which I think the S5 phone also has. When I switch this tablet into grayscale mode, the battery life is fantastic. When I go into Ultra-Powersaving mode, the tablet estimates over 7 weeks of standby time.
I have had the first samsung galaxy phone the s3 and now the s5 I am a fan of the samsung interface that you just cant get with other android phones I use my s5 for everything but as others have said keep it updated and enjoy the phone