I love the SIPs and how well they grow figs, but I've gotten away from them the last year or so. My reasons are pretty simple... space. They take up a lot of room in my garage and they are too heavy to stack on top of one another. They are also too heavy to do the fig shuffle with. If you have the room and the strength though, they grow figs better than anything else I've found. For now, I've started using tree pots with holes only in the side and burying them halfway in the ground. We will see how they work in comparison.
To address a few of the questions I saw... much like Dennis I've used landscape fabric and burlap and I have seen no difference. I can say by the second year, there is no burlap left (I haven't checked sooner to see how fast it degrades). I've experimented with plastic on top and plastic off. I believe the plastic helps in keeping the soil damp and allows a larger root ball to form. I haven't seen any serious degradation not using it either though. The only downside to not using it, is you get a lot of suckers. If you are trying to grow the fig into a tree and not a bush, it is more convenient to use the plastic covering. I use drip irrigation in my potted orchard and some SIPs I use a fill tube and some I do not... I don't think it matters either way as long as you water enough to fill the reservoir. I tried to root prune some of my 55g barrel cut in half SIPs last year and I couldn't get the tree out. It was just too heavy and too stuck in there. So I ended up using a sawz all and root pruning blade and cut sections of the root mass out and then filled in with fresh soil. It wasn't perfect, but seemed to work.