S4 is a great phone...no doubt. Great screen, if you like TouchWiz, it has all that and more. It has a great camera and captures very nice images. If you are already familiar with the UI of the tab3, you should feel right at home with the S4. It's snappy and very easy to use. It is loaded with very neat tools, and can be a very entertaining phone.
Unfortunately my experience was not indicative of the typical owner. I had an S4, and although I did like lots of things about it, I suffered from some issues...mainly battery issues and running hot all day. It would be fully charged at 8:00am and completely dead by 6:00pm most days. This was without even using it all day long, just sitting on the desk in rest mode. I wasn't running all kinds of crazy apps, just the mainstays. I wasn't rooted or modded in any way. I even did factory restores on it but the problems remained. Still every manufacturer comes out with a lemon or two...and for certain mine was.
When the most recent OTA update came out, my phone faithfully downloaded it, installed it and failed. Then after working with Verizon and using the suggested Samsung repair process, three times and the phone was completely dead...black screen, no activity whatsoever. Battery pull and replacement made no diff, and I had 2 other known good batteries to swap into it. Nothing seemed to resolve it, so I did a swap/upgrade to the Droid MAXX. Not as high a resolution screen, battery's not removable, no SD card slot, but the bigger battery and the very efficient X8 multiple-core processor system seems to fix the problems I was having.
So, I would be very watchful for any signs of heating up or battery drain. If you experience it, I would suggest getting in touch with Verizon quickly. Hopefully you don't have these problems. There are VERY FEW claims regarding this phone and problems similar to mine, but they're out there. Good luck! :biggrin: