I purchased these to add energy-efficiency to unlined dining room curtains during the winter months in Wisconsin.  The drapery panels are back-tab style and I was able to add the lining panels to the rod without difficulty.  They hang straight and are not visible from the room side.  
The lining panel is not as wide (48") as a flat curtain panel (54") and I assume that is because the liner is meant to be flexible to use with all types of panels, including pinch pleated curtains, whose finished width is more narrow.  Consequently, there will be some additional gathering at the header to fit.  There are also not enough loops to have one between every tab, but you could easily add more of your own, which I did.  I also tacked the corners of the liner to the curtain panel so the edges would lie flatter.

Pros: Practical and easy solution for unlined drapery panels.  Flexible for many styles.
Cons: Narrow width for standard flat-panel curtains.  Could use more loops on the header.