1- Display
Galaxy S4 has a very fine display and high pixel density which brings up smooth and fine display. Colors are nice and natural. I would say, one of the finest display i have ever seen on a smartphone.
2- Scrolling
When it comes to all kinds of scrolling, swapping Apps screens, scrolling through contacts, it is more smoother than old Galaxy models, of course, but there comes minor hangs sometime. Like when i scroll through phone book it sometimes get short stuck but they are not remarkable. Overall, scrolling is not as smooth as i expected!
3- Camera
Photos from 13 megapixel camera on S4, looks very clear, fine, smooth and detailed. Camera zoom enables you to zoom the image into its every detail. With build in filters and modes, you can have many different types of images. One cool feature i noticed is that, you can attach the audio of surrounding of your environment where you take your snapshot. And of course there are more features as you know. But there is one thing i noticed as unsatisfied, which is, camera colors are not as bright as Note 2 or iPhone 5 when you shoot with camera. Though, as i said, picture quality is far more better than these two devices as it should be.
4- Eye motion detect.
As you have seen on Samsung Ads, and all over the internet, S4 got a so called smart features, which is detecting your eye motion and control video playback. This feature is really no use and it does not work so well for me. I would say it as a gimmick more than a smart feature. Though, i am sure Samsung will improve it in future.
5- Smart scrolling
Smart scrolling feature, where you can scroll a web page with the actions of your fingers over screen, without touching screen, seems to be annoying. The response is slow and it feels me like, i am crazy, moving my hand over phone, am i doing a magic!!
Conclusion
Overall, i would say Samsung Galaxy S4 is great phone, with faster response and bright display. It operates more smoother when compared to other Samsung Galaxy family members as it should be. This phone is great if you love Samsung and Android, and looking for faster and ideal sized phone. It is thin and lightweight and great on hand. If you only want buy it for its "so called" smart functions, i would recommend you to not to buy it.