I've been using the BoomStick Trio for several months now, and to my surprise, my favorite is the champagne-colored highlighter, the Glimmer stick. (I also like the Glo moisturizer stick and the Color multiple, FWIW. I just like the Glimmer the best.)
Why am I surprised? For one, it's a cream highlighter, and I was devoted to my liquid Moonstone from BECCA. For two, it's a mauve-y champagne color in the stick, and I feared it would clash with my pale, warm-toned skin. But no: I pat it on my (nearly non-existent) cheekbones, blend gently, and I get a much more effective gleam than even Moonstone. I don't see lines of demarcation or a clash of undertones.
My favorite use, though, is as a dot on the eyelid just above the pupil, as Cindy demonstrates in a video on her site. This wakes up the neutral, mostly matte eye makeup I usually do without accentuating any creepiness on my eyelids. The Glimmer also doesn't seem to separate or crease particularly. Very nice.
Whether you think this is expensive depends on what you're comparing it to. This is $24 for 8 grams, which is $3/gram. The Stila convertible color is nearly twice as much, at $5.88/gram. The Benefit Watt's Up is $3.2/gram. The Nars Multiple (the original, not the matte) is slightly less, at $2.78/gram. The Burt's Bees Lip Shimmers (which could be used as a highlighters) are $2/gram. So the price seems to me to be in line with similar products.
As for the Moonstone? I use it mostly to mix with too-matte liquid foundations or to thin out cream ones.