I've yet to get my self a case for my S4. I'm still using the case that it came in for protection when I'm out playing and that's mainly because I didn't really like the original case that it was released with.
A couple of things that put me off was actually all bout the laptop stand. The concept of the built-in laptop stand built in to the case is brilliant in it self, but it also adds unnecessary weight and adds to the height of the case.
It also requires you to have alot of space behind you setup. Some DJ booths are cramped and then you would just have to take it off anyway.
I mainly don't like hardcases (even though their the best protection for your gear) simply because they are terrible to carry around for long distances. Once my arms get tired I tend to lean over to the side a bit and then the corners of the case start hitting my legs all the time.
There are some good cases for S4 on the market like the UDG Trolley bag. I've bought the other UDG bag which I just love. The quality and all over solution of the bag is simply magnificent.