First of all, I believe
this is the case being referenced, for those looking for a link.
I picked one of these up at Radio Shack back when I got my S4 (~$25 at the time I think). The selection of cases wasn't great at the time, but I wanted to get *something* on it because I know how clumsy I am.
On previous phones, I had been using Seidio Active cases, which I really liked for the amount of protection they provided, but never really liked the extra bulk that they added.
Frankly, I think it's a pretty decent case. It add minimal bulk, yet still makes the phone easier to grip and provides protection from minor falls and gives a slight lip over the screen surface which I like to prevent scratches if the phone were placed face down on a table or similar surface. Because it's made by Samsung, the fit is pretty much perfect, which is also a plus; and it's easy to put on and remove. As for negatives, it definitely doesn't provide as much protection as the Seidio Active case I had on my S3 did, but again, that's a sacrifice I was willing to make for a slimmer device to carry around in my pocket. The back is also a harder, smoother plastic, which on mine has gotten beat up a bit with scratches and such...so if you give high value to aesthetics and things looking like new (which I don't--the case is there to take the beating so my phone doesn't have to), then you should be aware of this.
All in all, I'd give 4 out of 5 stars. I'm certainly happy enough with it that I'm not going to go out looking for a replacement even though there are a lot more options out there now. I'm not 100% certain if I'd buy it again if I needed a new case today, but it would be on the short list of ones I'd consider.