User.cfg is located in your Piranha Games\MechWarrior Online folder.
It is exactly like an ordinary text file, and can be opened with any ordinary text editor.
What follows are a few of the more useful things that can be put into it:
i_mouse_smooth = <0 or 1> i_mouse_accel = <0 or 1>
This allows you to disable mouse accelleration ingame. If you don't know what mouse accelleration is, then you probably don't care about this. All it does is change the way your mouse behaves. Some people prefer mouse accelleration on, some people prefer mouse accelleration off.
cl_sensitivity = <decimal number between 0 and 1>
This allows you to scale your mouse's sensetivity. 1 means the mouse moves at completely normal speed, 0 means it doesn't move at all, .5 means it moves half as fast as it ordinarily might. This too is a matter of preference, and depends on how you aim. Lower numbers generally mean aiming is slower and more precise, but it's harder to move your view large distances to smack that pesky raven flanking you. Larger values, conversly, allow you to lock onto that raven more quickly (arm/torso twist speed limits still apply however), at the cost of having your reticle be a bit more jumpy and harder to control.
cl_fov = <number of degrees>
This controls how wide your field of view is. It can be anywhere between 0 and 179 degrees (180 degrees or more does not work). The larger it is, the more area you can see around you, but also causes distortion at the edges of your screen and makes things look smaller and farther away. Zooming ignores this, your zoomed-in fov is the same no matter what this parameter is.
e_MaxViewDistSpecLerp = <number between 0 and 1>
This controls the render distance relative to the map specs- 1 would be highest default quality for the map, 0 would be lowest default quality, .5 would be halfway between those. I haven't personally tested this, so post if you try this and it works for you!
e_MaxViewDistance = <number of meters>
This controls the maximum render distance for entities such as mechs, trees, street lights, and whatnot. I haven't personally tested this, so post if you try this and it works for you!
The following parameters have default values and require you to replace the default settings files before they will work in your user.cfg
e_ViewDistRatioCustom = <multiplier>
This controls the multiplier for the distance at which vehicles render to the distances at which infantry render. You can set this to 500 or something big to make mechs always render. I haven't personally tested this, so post if you try this and it works for you!
r_DepthOfField = <0 or 1>
This controls whether or not you have depth of field, which is the graphics effect that makes far-away things seem blurrier. It is off on low post-processing and on otherwise be default.
r_ColorGrading = <0 or 1>
This controls how color modification is done. Normally, all the colors are modified, and this usually causes things to have a desaturated look. Disabling this makes all the colors display exactly as they are. (Most notably, Caustic Valley looks more greenish than brownish).
The default settings can be found in Piranha Games\MechWarrior Online\Engine\Engine.pak\Config\CVarGroups and Piranha Games\MechWarrior Online\Engine\Engine.pak\Config\CVarGroupsMWO. (Engine.pak can be opened with most archiving programs, such as winrar or 7zip).
Copying the .cfg files located within to Piranha Games\MechWarrior Online\Engine\Config\CVarGroups(MWO) causes these new files to override the old ones.
You can then put a semicolon before any line in them to "comment them out" and cause them to become inactive, allowing the setting to be overridden in user.cfg.
For a full list of potentially modifiable parameters, consult the cryengine wiki.
This has been a public service announcement, informing the general public that such things exist for the sake of having a fair and even playing field for everyone.
Edited by Zapmunk, 23 February 2013 - 06:33 PM.