I like them! They look great. I can fit two figs per section, mostly. As you can see here, I've (mostly) put custom figs up front and an official fig in the back (the more impressive fig, so to speak, shown off). They even have openings in the back to a wall-mount via screws. They also stack snugly. Unfortunately the top studs are slightly larger than 4 regular studs, so building something to fit on top will take a bit more work than just building a base with a 4x4 hole in it.
This isn't the final display. I'll probably move the Firefly figs back out onto my shelf. And even when I do that I won't have room for ALL the Marvel figs (and with the chrome Star Wars figs, which definitely need to be protected from dust and fingerprints here, they take up more space from DC figs not housed here).
While I would love to get more, having these kind of cases to display everything I want to show off would get extremely pricey. I think the next step is to get some small display cases, like one might have for model cars (or a LEGO DeLorean) and actually build some step-like features with staggering steps and figs, like I already do:
(Also featured: Lots of figs.)
However, all in all, I really like these and have no regrets purchasing them. It's just a matter of deciding which figs get to live dust-free.