I use it and my comments would be that if you are going to move the pen every week or so it's fine. If not, you will either have to stop the grass growing under it or you will be in a world of pain. It does work, don't get me wrong and I think it has it's place. But. In the spring / summer the grass will grow up and short it out. You can try to stop this and many have with things like DPC etc. In the winter, it will blow over if you are anywhere exposed. If you do lapse and let the grass grow though it, you'll have a hell of a game removing it as it will grab it like steel.
I think the thing is, it's not the solution they say it is. If you look at someone like Joel Salatin who moves his hens every day, it's amazing. If you are looking to make a semi-permanent pen then you are going to have to think about the grass issue and also maybe put in a few proper posts at the corners and maybe one per side to hold it all up in really bad weather.
I haven't given up on it (yet) but I do also run a 5 strand polywire electric fence around the outside of my nets as double insurance. It's a really good product and does keep everything out, as long as it is working and upright. One pen may be manageable. I've got 9 and it's all getting a bit much to be honest!