I have quite a few, and I love using them to mix up new lipgloss colors. it kind of works like the shadebenders in that regard. I particularly like the gold one, because it has a HUGE impact on all my lipsticks and lipglosses.
The duo rose, i use everywhere...lips, eyes, and cheeks. On the cheeks though, I go with a super think layer, and pat some powder over to get rid of the sticky factor...