This is our second winter using window film and we are very excited to be doing so. It can be a tad tricky to apply without wrinkles. Nothing fatal, but you will have to spend more time with the hair dryer on windows where you left a wrinkle near the edge.
We're a lot better at it now. They go on faster. Two of us get one installed in about 15 minutes (that includes measuring the window, measuring and cutting the film, cleaning the window (since you won't be able to clean it on the inside till spring!), cleaning the edge around the window where you'll tape it up (so the tape will stick), putting up the double-stick tape, stretching the film over the tape and sticking it, cutting off any larger overhangs, and tightening it with a blow dryer.
It's hard to say _exactly_ how much it helps, but we have measured heating costs fairly carefully and tried to compensate for variations in outside temperature. We know for a fact that our home retained more heat on cooler but not frigid nights, meaning the furnace did not run at all on many nights with temperatures in the 30s.
This year we are covering the windows in the basement as well. Great stuff.
Short of buying new windows, which is on our list, but would be almost five thousand dollars, we're very pleased with the film and will continue to use it.
Gotcha: animals can be a problem. Not a huge one, but a problem. We have a dog and two cats. The cats will probably be responsible for about 20-30 tears over the winter. The dog will do one or two. The tears are trivial to fix with clear packing tape, so it's not really a problem as long as you catch them fairly soon. We've never missed a tear long enough for it to become a huge problem.
