Treasure Trayz are the luxury end of the token holder market. They look impressive, especially the fuzzy, flocked ones. The design conveys a sense of careful engineering, they feel durable, and they stack well.
The lids snap shut on all four sides. They feel very secure. Plenty of lip around the edges of the lid mean that it's still relatively easy to open the container.
The lid snaps into place on all four sides when placed under a bottom. Base and lide will easily stay connected if you store the lid under the base. Modest stacks of closed containers will stay stacked. I was able to dangle a stack of 6 empty, closed trays from the top.
While the lids are beautifully engineered, they bulge inward, meaning they're not very practical to use as cups themselves. Similarly, you can only slightly overfill the base; any significant overflow will block the lid from closing.
The irregularly shaped tokens from Harry Potter: Hogwarts Battle fit well and are easy to retrieve. (The Stonemaier Games Plastic Resource Containers also work, and can fit inside of the Hogwarts Battle box with its plastic insert in place.) The same is true of the resource tokens from Star Trek: Ascendancy.
The Treasure Trayz really shined on the Terraforming Mars resource cubes. They're large enough to comfortably hold all of a single color, and the shallow slope ensures they cubes don't pack into a dense, difficult to extract from grid.
The smooth curve of the base made it easy to remove pieces, but if the tray was relatively full of cubes, I found it easy to accidentally knock some out. I had this problem with the small, copper cubes from Terraforming Mars on a regular basis. Careful technique (reach in at the near edge and pull toward you, don't reach in the middle and grab), mostly eliminated the problem.
I don't know if they're worth the premium, but the fuzzy, flocked trays are pleasant to handle and look great. With some gold Terraforming Mars cubes piled in, they look positively lux.
Treasure Trayz also make trays which are divided in half for storing two different types of pieces in the same space. I've not tried them, as they're not generally available yet, but I look forward to them.
Despite their rugged design, Treasure Trayz are not something I'd recommend in general. For small numbers of things, Stonemaier Games offering is cheap and effective. For larger number of things, but not cubes, G33kbox's GB1 is cheap, effective, and easily available. That leaves Treasure Trayz two places to shine: large numbers of cubes, which neither competitor handles well, and when you just want your tokens to live in luxury.
Disclaimer: Two flocked trays arrived unsolicited with my order of six plain trays. I believe they were an apology for some shipping problems, but they were free from the manufacturer. To the best of my knowledge, the manufacturer did not know of my plans to review the trays.