Been testing the Primal Android app for a week now, and so far my experience has been great. It looks really good.
For me, it seems to run much smoother than Amethyst — for some reason?
On Amethyst, images just appear while scrolling down and it's a bit laggy. Usually, it takes a quick second (and sometimes longer) before the image has finally appeared.
On Primal, it seems like images are preloaded before I've even begun scrolling, so I get a much smoother experience. It feels a lot like Instagram, where images are usually already loaded before scrolling. It's super snappy. I like it!