Love that I can use my 600EX-RT's with this baby, only...
"Wireless operation of the Speedlite 600EX-RT is not supported."
It would be tempting to think that maybe what Canon really means is that the on-board flash cannot be used as a master. But then one would have to wonder why the ST-E2 is listed as compatible and the ST-E3 is not listed at all. Apparently optical wireless is supported while RF wireless is not—even though the ST-E3 was available at retail before the G1X II was even on the drawing board.
I would think that they mean the G1XII can't serve as a radio master to the 600E-RT. And it also seems like the G1XII can't serve as an optical master on its own (even though it should), although it can with the 580, 600, and ST-E2. And I assume that it can work with an attached ST-E3 or 600EX-RT to use them as radio masters. But none of that is clear.
It reminds me about their little blurb in announcing the new MR-14 II where they said it could remotely control a 600. The implication being that it was an RT master, when the reality is that it is an optical master and can consequently remotely control lots of flashes in addition to the 600.
Either Canon wants to play silly little games about their flashes or they just can't write this stuff clearly.
Canon 6d, t1i, 24-70/4L, 20/2.8, 28/1.8, 40/2.8, 50/1.8II, 100/2.8 macro, 70-300/4-5.6, g1x, 430exII, 90ex
Elan 7N with 28-105/3.5-4.5II, Rebel G with 35-70/3.5-4.5, A-1 with 28/2.8, 50/1.8, and 135/3.5