^ yah im pretty leary of any "super solution in a can"
they key to bubble wrap type stuff is to have an airspace on the heated side, which may be possible to create by covering the door w/ one layer, then cut furring strips of bubble wrap, then add a second layer. the greater the airspace, the greater the R value.
while I dont believe many of the outrageous R claims of 3/8 bubble wrap, but it does provide a decent radiant brrier- which will help some in winter to reflect heat back in, and maybe a few R's
I cover my basement windows w/ it in wintertime and it does help considerably.