Hardware: Coming from a dual core S4/1 GB of ram I can say this is a huge performance boost. I still close down apps from time to time, though thats mostly for battery saving purposes. I have yet to have this device hang up on me. (Note: Chrome occasionally hangs up, though thats a function of Chrome I suspect. No other apps have hung.) The antennas in this device are great as well. I'm a crazy ground dweller. I was getting 1-2 bars on my Razr M, 2-4 bars on this phone. For all I know they have the cell receiver, but I can tell you theres a marked improvement in the S4. Data rates remain constant though, around 7 up/7 down on New York City's oversaturated LTE network. Middling speakers, though quality headphones solve.
Display: Ill let a little Apple bias shine now - the Iphone 4S and 5 have half the resolution but are sharper and brighter than this phone could dream to be. Well, yes, more pixels is grand, but the iPhone display is simply better. That being said this is still an amazing display. I actually prefer AMOLEDs more vibrant colors. I have slight color blindness, so the popping colors really jive well with my broken ass eyeballs. Much like a TV you have some good control over the display settings. I go with the "Vibrant" preset cause, well, I love those poppy AMOLED colors. Theres a setting for every type though.
Software: This section both validates and invalidates this review. I dont know stock vs Touchwiz Android, so I wont win many Fandroids by admitting that but it also shows im not a Fandroid. I'd like to think I just like good phones. That said, the software on this phone is wunderbar. First off the missing software option: software buttons. Purists love having buttons taking up the bottom 10% of their screen, I hate it. Its why I got this phone. Your menu buttons should not be on the ! on screen! Ahem, anyway. Beyond that its as if Samsung said "to hell with minimalist Android" and fancied it up. I was able to familiarize myself with it pretty quickly based on previous experience. Verizon offers free classes on how to use Android if you're new to the system, at least they do here in NY, so that should help with the learning curve.
As for most of the new additions: I havent had much luck with them. Frankly they are pretty weaksauce - I am not going to flail crazily at my phone to answer it or have it pop popcorn, etc. One really awesome addition though is the Universal Remote Control app included WatchOn. Cant find your remote? Got your S4. At a sports bar where your waitress is taking 20 minutes to switch to the Mets? Got your S4. At your girlfriends place, entering hour 4 of an Americas Next Top Model marathon? Got your S4 (well, at least you can suggest the TV gods are insisting on a new show...) Android is developed enough that its smooth a babies behind. And widgets are why I can never go back to iOS. (Also, being able to drag and drop your music folder instead of librarying and syncing and dancing to the rain gods to get your library on your phone is much, much better.)
Battery: Battery is where this place REALLY shines. My sister has an S3, and maybe gets 12-14 hours of serious usage. I want a phone I can use all day, syncing with personal email, syncing with a battery gobbling proprietary work email app, at 70% brightness. Well, I got it. Sadly I cant paste in images here, but right now I am looking at 18 hours on battery, 4 hours of display usage, wifi+GPS on all day, and still at 20% battery. What else can I say? Well, if youre a road weary business traveler like me you have the option of second batteries and extended life batteries, though I find it rather unnecessary. This was my biggest area of concern going into this phone, and this is my favorite aspect of it right now.
Camera: This section is pending, as I have taken fewer than 100 pictures at this point. I will address to hot points of discussion though: the HDR on this phone so far seems fairly mediocre. That being said the "Night" mode on this phone is the best I have experienced ever. This phones weakness was supposed to be low lighting and I can say without question that the low light setting on the S4 renders these concerns moot. Been out a few times with this guy, and the night mode captures dimly lit bar pictures fast and clearly, flash free.