dunster, I too have stayed away from it because the June Tailor rulers use a very flexible plastic that I think would "give" too much as you run your rotary cutter along the lines. I think I can be much more accurate just moving my ruler and know I have a solid ruler edge to run the blade on.
I really wish they would make this in a firm and thick plastic like other Omnigrid or Olfa type rulers. That would be something to really get excited about.