We used the poly-rope which is the "cheap" solution. Installed it in Nov.. and did a small paddock (about an acre) with it. We used a plug in style Zareba injector, which works pretty well, we got the 25 mile one, because ultimately we want a 6 acre pasture (pasture, funny since we have nothing but trees/rocks right now).
Anyway... it keeps its tension pretty good. It's easy to install if you insulate it correctly. Tapping into it is simple, and extending a run is simple. They sell these connectors to butt two ends together which are worthless. Here's a hint, TIE THEM!
Here's what the stuff looks like, and honestly we've been more than happy with it... we test is every couple days to make sure it's still charged (once we unplugged it, and the horses were "stretching" over it to eat grass from the front yard, but nobody has challenged it yet).
Yep that's my horse staked out on the front lawn. He and his pasture-mate play hard, and this was after we divided the run-in, and the paddock so that he wouldn't be disturbed. He just injured his hoof, and we're trying to keep him calm all summer while he grows some hoof back. It took me about 2-3 hours to divide the run-in, and corner off a section of paddock.
You can see here how I divided the run-in