I'm a Pro8100 owner as well, and avid gamer, and can confirm Brian's times. I tried the Rock Band test on my PS3 through my Denon 1910 (no overlay) and I come in right at 17ms with the Reon disabled. When I enable it, I'm coming in at 23ms - 25ms, which still is quite respectable and probably wouldn't even be noticed by all but the most sensitive FPS twitch types.
Keep in mind that not all Reon's are created equal... The Pro8100 uses the HQV VX-210 (highest end Reon VX chip made). I think the only other projectors to use this same chip are the new JVC RS25 and RS35. The Reon equipped Epson and Mits models are using the chip that is one step down (VX-200). Many of the Reon equipped AVRs and Blu-Ray players are using the VX-50/51 chips, which aren't nearly as good, and I'm guess that was what was causing the lag in previous testing due to the single channel versus the two independent channels in the 200 series.