One thing I noted about the Simkin/Hurley and Crystal Caste dice is that they are basic cylinders with flattened faces the numbers can appear on. In short, you don't need to use every available surface. What you do need to do is make sure the die lands so that a single number appears on top, and that results are random.
As a matter of fact, you don't need flat faces, so long as the die doesn't 'land' between numbers. And that would be a matter of how the die is weighted.
But the greatest advantage of cylindrical dice is, depending on the size of the cylinder you could have dice with very large number ranges (d10,000 anybody?

).
The proper weighting can also be used to create dice that give a bell curve result. Such as a d16 numbered 3-18 that gives the same results as using 3d6.
For those who prefer dice that use every bit of the surface this could be adapted to spherical dice.
Carrying this even further, picture a cylindrical or spherical dice that that has a display coating on it. An advancement on the electronic 'paper' now being worked on. The result depending on a combination of the die's rolling and the workings of the electronics inside. Some models programmable. Lots of potential here.
Think of a future d20 system using dice that can be selectively weighted. Such as getting a 15 on a d20 that has a -3 bias. That is, it has a bias to giving a 1-17 on the roll, with a lower chance for an 18-20. And the bias can be adjusted.
It could also make loaning dice problematical.
"Sorry, you can't use this dice. It has a +5 bias and is keyed to my voice."
Tons of potential here.