After my first and only experience dealing with ToCAD, I bought a G1 green label as a back-up. (G1 that takes the 21mm.) Judging from the time and expense it took to simply replace a dented lens hood, I can only speculate that a serious service or repair on my G2, which will be needed at some point, will cost far more than buying a G1 back-up.
This system is all about the lenses. You will want the 21mm, can't remember the last time I took it off. Have fun finding and affording a black one, though.
Heads up on the batteries. Yes, there is a warning that the juice is low . . .then count one potato, two potato, and the camera is dead.