I have now installed it on two houses. I ordered it from https://www.atticfoil.com/. I also blew in a bunch of insulation, so it is hard to say exactly the effect of just the foil. However, my energy usage has been down by 30% for both June and July as compared to last year. Plus, my AC actually cools normally, instead of struggling all day and it still getting hotter inside.

The installation process is pretty simple, just cut it in long lengths and staple it to the rafters. However, it can be complicated to get it in all the nooks and crannies, depending on how your attic is laid out. I would recommend to start with the easiest areas first, then work your way to the more complicated sections. I installed mine in November and December to stay away from the summer heat.