I've got 20 of the Lee Valley hockey puck versions. I use them much more than I thought I would. I started with 4. Although I poo-poo'd the idea I do now free hand route using only the pucks to hold the material. I use them when a piece needs to rest on pre-finished surfaces when the work is ongoing. Rockler does frequently give their versions away as deal-closers so if you're not in a hurry, you could watch for that to try them out cheap.
Any sufficiently advanced technology is indistinguishable from magic.
- Arthur C. Clarke