I bought this to line a thin, sheer curtain - which was a mistake.  It didn't look good behind the curtain (which was a very specific style and needed a sheer liner)..  So I moved it into another room to line a heavier curtain.  That is perfect.   It is pitch black and the room is warmer.

Pros: Darkens room, insulates room
Cons: Too heavy to line a sheer curtain.