It is darker than pinch o' peach and has a nice non-glitter shimmer. It definitely is sheer.
Having just started delving into warmer colors, after years of wearing pinks and plums, Pinch o Peach was my 1st MAC blush. I love it. Its perfect on me. Less than a month after my 1st MAC blush, the sheertone shimmer blushes are out, and I zipped up to my nearest MAC counter on the 1st day they were out.
Peachykeen's base color is similar to Pinch o Peach, but this is a warm peach with hints of pink and subtle gold shimmer. Of the 3 blushes I bought,Foolish Me and Plum Foolery the other 2, Peachykeen is the sheerest, so its easy to layer, easy to control the intensity.
As a comparison, Nar's Orgasm is much warmer on my skin, and loads more shimmer. So while Orgasm might be good for evenings, Peachykeen is a nice daytime look.
I'm a MAC NC25.