The Havalon system is a fantastic concept. I purchased the Piranta Tracer-22 in July '09 and although I have not used it to partially cape a deer, it has been used for taking meat, retrieving projectiles and hanging up foxes.
In preparation for next year I recently purchased some extra blades - one hundred #60XT and one hundred #22 blades for US$24 and US$29 respectively. That should see me through the year.