Upon opening a large case, you'll find three loose pieces of foam, to be fair, it is a little thin and I am concerned about how well it'll hold heavy pewter figures in place. But, I attempted it anyways, I managed to cram around 24 figures in a case, more or less will depend on the style of the figures. My test batch were my Chronopia Elves.
The Smaller cases are only gonna hold half that with two thin pieces of foam, they are a good size for holding a Song of Blades and Heroes warband, or perhaps a Mordhiem warband. The foam inserts are also very thin.
I am considering gluing the inserts into place as the flop around VERY loosely, this may help their stability a bit.
Now, there are some neat things about these, they look nice, especially since you can print your own sleeves (well when they upload them) you can also design your own, which is what I intend to do. They are a good price point, $10 for 4 cases, each holding 24 figures, that is 96 figures, not too bad at all. The cases do fit nicely into a messenger bag (Sorry Mantic, I already got a really nice one for $15, holds more stuff too . . . . ) I can probably fit around 6 cases and have space for my rulebooks army rosters, etc.
Should you buy them, well, that's up to you, will I get more, yeah, probably.
EDIT: I have whipped up a few inserts to use for my personal collection, they are not the best in the world, but I can tell what is in the boxes now, and in a fairly attractive fashion. Gives you an idea of what they'd look like on the shelf as well.
Finally, a TMPer requested the dimensions, so here are the dimensions roughly.