a decent option in between the all out sleeving and then the electrical tape is to use the stuff that you use putting amps in cars. radio shack calls it split tubing.
I use this when I build computers for other people. Looks clean, but doesn't take to long to do. I try to route as many power cables as I can behind the mobo tray as well. Then anything that has to show in the front of the case I put this split tubing on. I just get some zip ties to match whatever color i use.