As you'd want and expect, this flash sync cord allows you a greater degree of flexibility when using your Speedlight. Instead of being stuck on top of your camera, you're free to position your flash wherever you like in relation to your subject. This not only gives you control of which direction your shadows will go. It also lets you position the Speedlight closer or further away as well as making bounce flash much quicker and easier, no holding in buttons to rotate that flash head anymore! Just point it where you need it.
Although the SC-29 does everything that I would expect of it; I have to admit that it is quite expensive. A fair bit more than I would expect to pay for a cord to be honest. But you do get quality for your money including a handy locking male connector for the safety of you and your gear.
The only other downside is that by holding your flash in one hand, you only have one hand left for your camera, which can cause problems with operating your cameras controls. If you're handholding, it can also make holding the camera still quite difficult.
One last thing that you may be wondering is: is it worth my money to go for the SC-29 instead of the cheaper SC-28? The difference being that the SC-29 has a built in AutoFocus Illuminator and the SC-28 does not.
I have both sync cords and I would probably say no. If you shoot subjects that frequently give your cameras AF problems then you may benefit from the AF illuminator but personally my D300 has never had any such problems and I rarely use the AF assist when on camera or off so I would say: if cost is an issue then save yourself the slight difference in price and go for the 99% identical SC-28.