How are they valuable to education?

In a drafting or building construction class the 2D drawings can be brought to 3D form on a better scale.

We're putting one into our office "innovation room" to encourage prototyping of hardware ideas. It may be the best thing ever, or a waste of time, but we won't know until we find out

it's a puzzle in 3 dimensions:
how do you print a jack?

drawing leads to drawing things
drawing things leads to wanting to build things
building things leads to needing a way to make the parts

print signatures so they can be taken to the shop and cast in aluminum

print boats and bricks with the same volume of material to demonstrate what makes something buoyant

print parts for rubberband powered planes - the really slow flying ones might be good examples of science stuff

Lots of good ideas, but whether or not they learn from it depends a lot on the teacher. How will you use it? Better yet, have them come up with the ideas and figure out how best to use it.

There's a great project in itself.

How will you use it to engage their imaginations? Or might using it be a reward for learning what they need to know to use it well?