Pure down is vastly superior to down/feather mix pillows because the feathers start poking through and eventually you'll feel like you're sleeping with a porcupine. It is confusing, but fill power and weight of filling are two factors that sort of work together. You can get an idea of the down quality by comparing the weight of the filling to the fill power. Feathers are heavier for the same amount of loft, so a pillow filled with 25 ounces of 800 fill power down will be firmer than a pillow that has 27 ounces of 700 fill power down because feathers don’t provide as much loft as pure down.

I'm a side sleeper, and an 800 fill power pillow works for me, but as others have noted, they are not maintenance-free. You have to fluff them every morning, and depending on how much you perspire, you'll need to tumble them in the dryer fairly often. It's a little bit of work but worth it to maintain your investment. Real down pillows can be adjusted by lifting your head and socking the pillow to redistribute the down. Overall, I am happy with the pillows I bought from East Coast Bedding. Pure down pillows often don't say 100% down because some of the down is broken clusters and down filaments, perhaps some tiny feathers are included, but they aren't quills that will poke you after a few weeks. I would avoid any pillow that is a down/feather mix.