They really work well to cup a round bead in a design when making an angle. With a pearl or druk, when designing a curve, the demi round really aids in the look and function of the design. I used both the Demi 11 & 8 in this design called Arabella. Arabella works equally well with Paisley Duo and Zoliduo beads.
For a pretty chain, called the Bicycle Chain, I prefer the Demi 8 to the "O" bead often used for this chain. The smaller size works up easier to get the stitching nice and keep tension tight. I use the Demi size 8 with a size 15 seed bead replacing the "O" bead and size 11 seed bead. It really is a sweet chain for this sparkling pendant.