This issue is really annoying. And it's very specific. I've seen multiple threads about this elsewhere, so I know I'm not the only one suffering. The problem is as follows:

In third person mode, the WASD movement keys take about 0.5 seconds to react. Nothing else lags. Attack animations, jump etc, are all fine in third person. In first person, everything responds perfectly, including movement. The issue is literally just with third person movement.

I just upgraded my system, so I know it's not a power issue. I do have some mods installed, but it happens even when running a totally vanilla game. I've tried various combinations of forcing vync on and off, turning on triple buffering, and limiting frames, but the thing is, these are all approaches for general input lag. This is much more specific than that. Third person movement only. It's very confusing.

Anyone have any insight?

Try turning off the Rumble and Gamepad in the controls settings. It also helps to set these two lines in the Prefs file to look like this:

bGamepadEnable=0

bGamePadRumble=0

The above two lines are not together. However, just below the last one is this line, which you may or may not want to set to 0.

bMouseAcceleration=1

There are also values to change if you like this feature. It depends on your mouse really.

Didn't help unfortunately. Thanks though.

I'm starting to wonder if this is just the way the game is, and a lot of people either don't use first person, or don't notice. My system is brand new, top of the line, my install of windows is fresh, and it's such a specific issue. Like I said, I've seen people complaining elsewhere about it. See:

http://gaming.stackexchange.com/questions/86342/input-lag-when-in-third-person

http://forums.steampowered.com/forums/showthread.php?t=2226101

http://forums.nexusmods.com/index.php?/topic/554019-3rd-person-lag-movement/

http://forums.nexusmods.com/index.php?/topic/516904-3rd-person-movement-delay/

http://www.gamesas.com/third-person-movement-delay-t276732.html

http://steamcommunity.com/app/72850/discussions/0/846957366686018116/