
I've seen them only in pictures from other tile setters and from what I have seen they are an awesome alternative for something between (ugh, that looks dated) 12x12 granite tiles and (wow, that's expensive) granite slabs.
I say go for it. I was considering them in my own kitchen remodel but could not find a local source, everybody I ever asked just looked at me funny, nobody had any idea what I was talking about.
The best versions I've seen have used some creative cutting, like 45ing them where a peninsula and a counter top meet in the corner, they used the grout lines to their advantage, kind of ended up making a diamond pattern in the corner, hard to explain you would have to see it. I would do the same thing on an island, try to get away from a grid as much as possible.
I tried to find some pictures but I can't even find them.
I don't see any problems other than the normal ones that come with larger tiles, and that's the thinset taking a long time to dry and the issues of lippage being more dramatic, which is the case of any large tile.