I've been thinking of buying the kit to be honest but I think if I can pull off my own implementation, then it helps me learn the inner workings of a shooter.
I agree in writing your own system. I had this kit for a while when it was selling for $10-15. I think the author of this kit is writing his own online solution. Its a good kit; however, its very heavy on the CPU and hard to follow. Through my experience, most people who have downloaded my games, their devices/computers are much weaker than the device I've prototyped my game on. Also, in this kit everything inherits from something, which isn't a bad thing. I just had a hard time following where some of the variables originated from without opening three or four different scripts and scouring lines and lines of code.
Another issue you have when you use drop in prefabs like this, is that all the dependencies follow you into your scene and builds. Once you drop this prefab in your scene, even if you only want to use a small section of this and nothing else, your still going to have all the textures, effects, sounds associated with that prefab. I like to use UFPS more of a reference and learning tool, than a final solution. Of course, thats just personal preference.