I've done an input lag test on the VIZIO E3D420VX...
Benchmark: No input lag
This is what the lag test produced on my old CRT television. As the picture illustrates the input lag is almost non existent.

Input lag on the Vizio was locked at 50ms.
Note: my laptop was connected via HDMI and set to output @ 1280x720 which is not the native resolution of this television so these results might be improved with a 1920x1080 source.
The vizio was setup as follows...
Picture: Game/More/Advanced Picture:
All turned OFF
Settings/Game Mode:
ON
Something worth noting: If you are experiencing lag of upwards of 150 ms while gaming, (the controls will feel VERY floaty, easily noticeable if FPS's or fighting games) try turning the Settings/Game Mode: to OFF then turn Game Mode back ON. I was experiencing lag for about a week and was ready to give up on the TV... Then I decided to try this and it worked like a charm.
Games that I've played in 3D are:
Xbox:
COD:BO
PS3:
Killzone 3 (demo)
Motorstorm: Apocalypse (demo)
Super Stardust HD (demo)
Wipeout HD
Also, I saw the trailer for Uncharted 3 Drakes Deception (wow this is going to be amazing)
Movies watched in 3D thus far...
Mars Needs Moms (great sense of depth)
Despicable Me (my kids love this one)
The 3D capabilities of this television are not the sort that pop out of the screen at you, its more like looking through a window into another dimension. That's the best way I can describe it. What more can I say, I am completely blown away by this television and passive 3D in general. The screen uniformity is very good with no clouding to speak of. The black levels could be better I suppose. All things considered this is a great television that should be considered if your in the marked for a 3D tv.