Well, Flawless Pink is designed to be opaque and therefore it has a couple of nuances that you may want to be aware of to avoid problems.
If you work with multiple beads (like 99% of the world) multiple beads of Flawless Pink may look funky next to each other. The reason being is that there is soooo much pimgment in the powder that it is difficult to pick up 2 beads that have the same quantities of pigment in them because It is very difficult to always get the exact same ratio every time you pick up a bead. A small difference in your ratio (wet or dry) can lead to colouration matching problems even though your mix is still medium wet. This is similar to using multiple beads of White next to each other.
The other thing that the heavy pigmentation does is alter the feel of the bead slightly (kind of like the diff between Perfect Color White and Perfect Color Pink).
The other thing that can throw the look of FP, is the colouration and opacity of the clients natural nail plate.
The further away from the colouration of FP (whether from natural colouration to nail plate thickness) the more off the FP application will look. This is where custom blending with the Mosaics come into play.
All in all FP is a great product designed for makeover work (extending beds, etc) and for people who would custom blend colours for this job as it gives you a great head start doing this. It is not a great product to simply replace Perfect Colour Pink with though.
Hope this helps out