H & M Cha Cha was the first one I tried because there was sunshine when I started swatching, and there's no better polish for sunny weather than a holo. Application was fine; two coats over a base coat was good, and I skipped top coat because this was a swatching session. Indoors, in indirect light, Cha Cha is a slightly sparkly champagne color.
Outside in the sunshine the colors come out to play.
I decided to compare Cha Cha to another holo in my stash, OPI DS Classic, the polish I call my "office holo" because it's not too flashy for a customer meeting but very entertaining sitting in the sun at stoplights on my commute. Two coats of DS Classic was a bit less opaque than two coats of Cha Cha. DS Classic is a little warmer-toned and a little deeper-hued.
Outside, it was clear that the H & M is a finer grained and slightly less flamboyant holo, though they're both pretty.
I think Cha Cha might be my new office holo. Thanks, Miranda!