For me, there is no noticeable input lag in Game mode on the EX720. I played some Bad Company 2 online and HL2 to check, and it didn't feel off to me. Once you try to enable Motionflow or the likes, that's another story.
I also have the new 3D glasses here. However, since I never owned the previous ones, nor have I checked 3D on other TVs I can't really compare them. I still need to get my hands on some proper 3D content. What I can say, is that, as was mentioned, the 3D effect starts to disappear once you tilt your head, with that said, it didn't feel like I needed to sit myself in a specific position to get it right, so it's much of an issue, I think. On the upside, the image gets brighter, instead of darker.
Overall, it doesn't feel too dark in 3D. I tried it out during day time, with sun shining through my window, and it didn't bother me at all. If you tilt your head, you will see that the difference in lighting is substantial (although you need to consider that backlight is maxed out in 3D mode), but if you avoid that, it seems good enough. There is an option to adjust the brightness of the glasses. But I am not sure why you'd want to set it to anything but "High"
As for crosstalk, as I have said, I need to get some proper 3D content, but it seems that objects closer to the top of the screen (starting from somewhere around a third of the screen from the top) show some noticeable crosstalk, while everything below that looks great, but it seems inconsistent in that regard so far - sometimes it looks perfect.
I need to get Avatar in 3D and see what that gives me