First, let me say, I don't work for Samsung, AT&T, or anyone else for that matter. I'm just a stay at home mom who has had a lot of experience with phones, especially Samsung phones. I had my S3 for a long time and loved it, but when because of coverage issues we decided to switched to AT&T, I opted for the S4, despite some of the scathing reviews it received by some. Let me address some of the major issues ppl seem to bring up and the solutions:
Battery: I have had no trouble with the battery life. In fact, I'm pretty impressed with it compared to the S3, which was a major improvement over the previous two smartphones I had owned. I've been using it all day, over 12 hours, heavy texting and reading. Still at 60%. Turn the brightness down on your phone when you're indoors (which is most of the time), and turn on Power Saving mode in the pull down bar. Its that simple, people. Check the task manager now and again and clear the memory. That's it.
SD card: If you're having trouble with an SD card, go talk to the people at the AT&T store. They can help you figure out if the card itself is defective or if perhaps the phone has a defect, in either case, you should be able to get a replacement, depending on where you bought the SD card. I'm using the same SD card that came with my Samsung Galaxy S Mezmerize (ancient history now, right?), and this is the third phone I've had it in. Works perfect with no problems.
"Gimicky" Features: If you don't like them/don't use them, turn them off. I for one don't need some of the very ones that reviews say are the only ones they see a need for. The Air Gesture, for example, is a neat thing for people who have their hands dirty all the time in the kitchen (like me), or at their job, and they don't want that all over their phone. There's something for everyone, and you can just pick and choose what you want.
Plastic build: So it's not made of metal like the HTC One or an iPhone. OK. Admitted. But the polycarbonate build is pretty strong and would take quite a beating on it's own, not to mention the Gorilla Glass. But, personally, I use an Otterbox, and I would no matter what kind of phone I had. I dropped my Galaxy S3 hundreds of times in my Otterbox, no damage whatsoever. Best $$$ ever spent. Otterbox is a great American company with American made products. Just stick it in an Otterbox and quit worrying about the plastic.
Camera: I hear mixed reviews on the camera, and I wonder why. Its an awesome camera. Make sure you take the small plastic protective film off the camera lens when you take it out of the box. That could be the main reason people have problems with picture quality. I know I almost missed it.
Large "Unmoveable" Widgets on the homescreens: This one is simple. If there's something on your homescreen you don't like or don't want there, hold your finger down on it until the screen changes to allow you to move it. Then, put it where you want it on that page or move it to the far right or left to move it to another page, or move it to the top of the screen to the little trash can to delete it. Easy peasy.
I think that about covers it. The Galaxy S4 is an awesome, well-made phone. It performs well, and it extremely customizable. It also puts me at ease knowing that Samsung makes the lowest radiation output phones on the market, so consider that if that is a concern to you.