I was recently sent for review a free sample of the so-called "AmericaStone", a small ceramic sharpening stone with three surfaces that claims to deburr, hone and polish a blade's edge, and handle serrations too. There's a demonstration video on YouTube that illustrates it in action.
I've given the Americastone a workout over the past few weeks, on everything from folding knives, to sheath knives, to machetes, and on blades that were smooth, or nicked, or rusted. It does a good job sharpening them all, but its small size means that it takes a while to get anything but a small blade into sharp condition, and also makes it more difficult to work on nicks and flats in the blade. A larger, bench version of this stone would help deal with those issues, but at present it's only made in one size. (Using the Americastone on a machete or axe is an exercise in frustration - tiny tool meets very large blade! Clearly, it's not designed for such use. A big, coarse tool such as the Sharpal 216N or Lansky Puck is far more suitable.)
After using the Americastone fairly extensively, I'm in two minds about it. It works very well at what it does; but it works slowly, and in the field, one can't always spare the time for that. If speed is an important factor, most of us would be better served by a pocket sharpener such as those from Sharpal, Lansky or Smith's (which are also a third of the price of the Americastone). The latter will still be useful as a finishing stone for use at leisure, but not as a primary sharpener under those circumstances.
I should also point out that I was raised in Africa. We had different priorities there when it came to field knives, as we've discussed before in these (and other) articles:
I think that, for a rough field environment, the Americastone would not be as useful as a coarser, more general-purpose instrument. However, for a knife aficionado working at home or in town, who wants to keep his high-quality blades razor-sharp and doesn't mind taking the time and the trouble to do so, it's a useful and highly portable tool.
(Despite the fact that the stone I was sent was a free sample, I didn't allow that to influence my review of it, as you can see for yourselves.)