I've bought two of the three new pots, Waystone Green and Spiritstone Red, to try out, and see how it compares to my usual technique.
Firstly these two paints are a bit thicker than normal paints (especially the red): not base colour or textured thick, but fairly gelatinous compared to normal colours. This would mean that for smaller parts you only need a tiny amount. The best way I can describe these paints is that they're a mix of a glaze and gloss varnish. They'll tint whatever you paint with that colour, and leave a very smooth, shiny coat.
On my Contemptor, I've tried painting them over a bright like-for-like colour (Goblin green for Waystone and Evil Sunz Scarlet with some orange for Spiritstone) for more stone-like effects (i'd say the previous efforts give a glass-like effect . I'd argue that this yields much better, realistic results, especially if you want darker looking stones. I think of the two I've tried the red gems look better, but this is a technique which will be refined.
In some lights I'd say you get a better shine than a normal gloss coat over the top. the red stones look fantastic when the light catches them.
In the end I've found that you get similar results to painting gems the old fashioned way, but it's a lot quicker and easier. So if you're after a fast way to paint effective looking gemstones, then these new technical paints are a good option. If you've already mastered a technique then this doesn't really achieve anything different, but if you want to try something new, give these paints a go.