I have the Cactus V2's, but it's quite difficult to use and a huge learning curve.
Everything had to be done in Manual mode, and instead of shooting how you normally would, you have to shoot to the flash.

Now you have to throw in flash compensation, exposure etc. as well as getting the shot to come out.
It's difficult, my first few shots with it were just plain white. lol!

Does the flash extension just work like the flash is sitting on top of the camera?

You should have a flash light meter if you use the flash manually. Yea ETTL works normally with the cord, so its same as having flash on camera. Its handy when you want to use flash on other hand and camera on other, but with tripod i would definetly use wireless transimmer instead. Its quite easy just to put power down from the flash with the cord tho to get good lights, with these i used -2 power.

Whats the cable's model name? I'm going to go buy one lol.