A saint wrote:

Here is what I did to fix mouse acceleration (and have it save my changes). I'd imagine this could be used to make other configuration edits as well.

You're going to be adding the following lines to the [Controls] section of various .ini files.

fForegroundMouseAccelBase=0
fForegroundMouseAccelTop=0
fForegroundMouseBase=0
fForegroundMouseMult=0

First, go to DocumentsMy GamesFalloutNV. You will be editing both Fallout.ini and FalloutPrefs.ini. Make sure they are not read-only.

Then go to Program FilesSteamsteamappscommonfallout new vegas. Edit Fallout_default.ini. Again, make sure it is not read-only.

Finally, go to Program FilesSteamuserdata. You should see a folder named some random combination of numbers. In that folder, you'll see a bunch of other folders with number names. Sort by last modified, and open the most recently modified folder (except config). In that folder, you should see falloutprefs.ini. Edit that one. If you do all that, changes should stick. It's worked for me so far. This is all without disabling Steam Cloud or anything like that.