Nice ideas Water Music. Transparency sliders would be interesting. If layer selection is implemented then all you'd need is a single slider along the bottom of the row of buttons. Vertices/edges/faces visibility would be cool also, I wonder if that'd be much more difficult to implement.
Some more feedback from me as well.
Turns out you can select a shape (or vertex, edge, whatever), hide the layer, and still manipulate them while they are invisible. I think it might be better to deselect or disable the content in hidden layers so that unintended actions don't occur if someone leaves something selected by accident.
The lock mechanism seems incomplete. You can select a shape, then lock it, and then manipulate it still. Point edit operations also seem to affect the content within locked layers. I think layers will become a powerful tool if a locked layer is absolutely, totally locked. Also, I think it would be wonderful if locked layers don't show the points in point-edit mode, or maybe put a locked layer GUI option set in Configure->GUI? Or Options->Layer dialog options for GUI settings on a per-layer basis?
I know we're kinda adding a ton of ideas onto this. Layers can have a lot of features to them, and some people might want more or less depending on what the layer's being used for. Personally, I'd like to know what your vision for layers is, Steve.