This also introduces crosstalk to the cable, as data wires that were separated by grounds are now right next to each other. This isn't a problem for mode 1-mode 4 drives, but it can interfere with UDMA 33. Definately do not do this to UDMA 66 or 100... Even if you don't rip the cable to buggery, the added crostalk will stop the cable from being able to run at 66... not to mention that 66 cables are thinner and get in the way less. I'd recommend splitting the cables into strips of even numbers of wires, to keep every conductor with its ground, and bundling the strips like this \/\/\, rather then this \\\\\, which should keep the data wires away from each other.

Another nice trick, if you have a master and a slave drive right on top of each other, with their connectors on opposite sides, or one drive mounted vertically, the other horizontally, it can be difficult to plug both devices in, as the cable doesn't bend very easily. If you split the cable into strips of 4 or 6 wires, but don't bother taping it will make the cable a lot more flexible along its parallel axis, hopefully allowing it to be plugged in. As a final solution, shredding the cable into pairs allows it to negitiate extreme bends.

Finally, 'round cables' can be cable-tied to the case to keep them out the way. Much neater than ribbon cables.