3. I've been told the sharper and cleaner the edges of a die the better. Is this actually true for most people?
Technically speaking, it's not the sharpness of the edge that's important, it's the precision. An edge that is more rounded will allow the die to roll more. If all edges are rounded exactly the same, all sides will still be equally likely to roll and the die will be true. But if one edge is rounded more than another, the results of the die will be skewed.
Sharp edges are simply the easiest way to ensure equal roundness. It's a pain in the butt to QA curvature of an edge to the same precision you can measure sharpness. In practice, most round edges are a result of tumbling the dice as part of the manufacturing process, which gives almost no control over the evenness of the rounding. Also, sharp edges make it easier for users to feel the die and easily tell if one side is more rounded due to wear or tampering (this is a bigger deal for gambling dice than D+D, but YMMV).
But if you're custom-machining your own dice, you could theoretically control the process of machining rounded edges to make sure it's consistent. This would allow you to avoid the problems with sharp edges, like the fact that they're less comfy in your hands, really hurt to step on, and can damage the rolling surface.
All that being said, I doubt I would ever buy metal dice. In addition to being heavier and harsher like people have mentioned, metal is also more volatile and would tend not age as well.
