I've been playing with my Zen a lot over the last year or so, and I've made (or added) a few additions that have made using it much more fun.
1. A permanently connected Z-axis touch off plate. Just a scrap of .26" thick aluminum, a self-tapping screw and 2 pieces of wire, but what a difference to repeatably. This has got to be a tie for the best thing I've done to my Zen (other than the new spoil board). Make getting a job set up so easy, and I love seeing the cuts finish JUST above the spoil board. Ran one wire to my spindle, the other to the aluminum plate.
2. A jog pendant. Lucked on the same model USB game controller that the guy used here (http://wiki.linuxcnc.org/cgi-bin/wiki.p ... te_Pendant), put his changes into my configs, and bing-bang, I've got a remote jog capability at three speeds. The controls are a little bit not what I would have chosen myself, but it's alright, I can live with it for now.