I bought one of these at Comic-Con last week. Koto was charging $10 for a single tray, R2 or Han, I chose Han. They're silicone, have 6 smaller slots, and one big slot. I just ran my first batch of Carbonite slabs, and they look great! I don't know how to get my ice to freeze fast enough to be clear so they're cloudy in areas, but the surface details are very nice (make sure to use a slow stream of water to avoid air bubbles trapping at the bottom, that will affect features). The little ones lose their details pretty fast, but the big cube is still quite recognizable. There are no side details on Han's carbonite slab, the cubes wouldn't loosen from the tray if there were, but the surface looks spot on in both sizes. I'm considering buying more Han trays, this is really enough ice for just 1 cold drink, or 2 mild drinks, not enough for entertaining even one guest if you're having a bev too.
The next ones up I believe are the Death Star and the X-wing. The Death Star I think will be an easy sell for me, the X-wing not as much only because the thin shape will melt faster.
BTW, as I've been writing this, the big Han ice cube has held up amazingly well, my drink is half gone and the surface features are still clearly present, Han's gruesomely-posed hands just barely poking above the beverage line. I just investigated the little ones better, they've actually held some details, they are just smaller and harder to see with the cloudiness common to home-made ice cubes. I suspect the ones that held details better were closer to the big daddy ice cube.
All in all, Koto has a winner on their hands with this item. Yay! I just realized that this was the ONLY Star Wars purchase I made at Comic-Con, how weird.