I saw this in action in Japan, as Kow Yokoyama uses it (Calls it his "lightsaber"). It's a little scary to think it'd cut the CRAP out of a finger... but then again, since you don't need to bear down with weight to make a cut (besides enough to control it, like you would on a jigsaw), the chances of a blade jumping out or off of your object and into skin are greatly reduced. I'm famous for doing that, so hopefully I can avoid stitches from now on, heh.
Trimming resin away from pour stubs will be a cinch now!
YouTube - USW-334 Ultrasonic cutter
Trimming resin away from pour stubs will be a cinch now!
YouTube - USW-334 Ultrasonic cutter