For those complaining about the stock keyboard lacking autocorrect, from what I've read around the forum, that is a direct function of the Apple lawsuit.
Solution: install SwiftKey as mentioned above and finetune the long press to ~200 ms. I no longer miss the number keys on top.
Technically, the eye scrolling feature is mis-named. It is face or head scrolling. Keep your eyes fixed on the screen and move your head up or down and see what happens.
I find some of the motion features to be hit or miss... but some of them appear solid too. One I've had trouble with is getting the GS4 to answer a call with a hand motion... a handy feature (if it works) when cooking or changing the oil in the car or whatever.
I use Nova Prime (which negates that nice ability to move an app to a target screen). But that's a very minor nit to pick. I've also disabled much of the bloatware that I won't use and turned off animation in developer mode. Lag? What's that?
And my new favorite case is the Speck CandyShell Grip!
What case are you gonna put on this one twister6?