If you are thinking about buying this bit of kit, don’t.
I’m serious, don’t even consider it. It’s over priced, unreliable and its inception has resulted in Nikon deliberately crippling their speed lights to force photographers to use this rather than a 3rd party system. To ‘encourage’ photographers to use the SU800 Nikon removed the TTL quench pin from their more recent flashes (and killed some backwards compatibility with their older film cameras along with it!) meaning that if you want to shoot TTL you have to use the SU800. For what it is worth I don’t shoot TTL anyway, to me TTL is to flash what auto is to exposure, but even so it is not a cool move by Nikon.
The SU-800’s main fault is it reliance on infra red rather than radio waves. This means you have to have a line-of-site between you and the ridiculously small receiver on the flash and the signal is easily over powered by the sun. The advertised range of 20m is fanciful at best (I have known the unit struggle with 8m in overcast light) and the narrow trigger beam means that the flash has to be in front of the camera, so you can forget about any fancy lighting set-up. It really isn’t fit for purpose.
Luckily there are plenty of excellent alternatives. The Radio Popper series have proven to be very rugged and I have heard great things about the PocketWizard triggers as well. Of course you don’t have to spend anything like that much cash, there are plenty of cheap triggers available but I don’t mind spending a bit more for the reliability it brings.