So much easier than I anticipated. And the results are better too. I grew up not being able to see through the plastic but this stuff is like looking through glass.
I did find it to have a static cling so be careful where you are laying it out when making your cuts.
I found it helpful to attach the top, bottom, and then sides. In that order, while tugging at the edges, I got a much less wrinkled finish.
The kit cost $11. I hope I get that much savings in heat.
I have yet to do my living room window because I need a piece of trim at the bottom of the window. Not only will this give me a place to adhere the plastic, but I will also cut out the draft that comes from the gap in the plaster and the frame of the window. I think this window will make the most significant difference in the efficiency of heating our home.