Whether or not you are wasting your time is up to you. No one can decide that for you.
Personally, I choose to go the custom route because I'm not content with stock cabling. The cables that plug into the power supply use standard ATX female pins, so you can easily remove the pins, make your own cable, and plug it into the power supply. For example,
here is a cable that I made for a fan controller that plugs directly into the power supply. I've
made two for the hard drive backplanes on my server (you can see the colored cables in the bottom right of the picture).
I even had someone send me a Corsair AX1200 to have a bunch of custom cables done.
http://thideras.com/images/cables/SeeThruHead/seethruhead_cables_07.JPG
http://thideras.com/images/cables/SeeThruHead/seethruhead_cables_08.JPG
http://thideras.com/images/cables/SeeThruHead/seethruhead_cables_09.JPG
http://thideras.com/images/cables/SeeThruHead/seethruhead_cables_10.JPG
http://thideras.com/images/cables/SeeThruHead/seethruhead_cables_11.JPG
As long as you have the tools, dedication, and knowledge, you can make pretty much any cable you want.