If you have the money get the better version.
I own the 2011 46C7000 first gen 3D model and its awesome for gaming, the game mode eliminate he lag..
I use SPDIF for audio, so in cases of lag its very easy to notice because the processing is separate and I never experienced any issues with lag...
The 3D is fine and yours should be better since the E series is newer then my C series
Also you will be able to play full 3D PC quality games on your TV without a console, Samsung just signed up with Gaikai, they will be releasing a TV app that will stream video games, so you just need to connect a gamepad to your TV and you will be able to play lots of games in full HD and PC quality.
Well it also depends on your location and internet speed, it worked fine on my 30Mb connection, tested need for speed in a browser window