1. Go to the installation folder.
2. Open Fallout_default.ini
3. Find the section: [Controls]
4. Add these lines:

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

If you for some reason are not playing on current steam patch, edit fallout.ini in the my documents/my games folder.

Is mouse acceleration necessarily bad to the run?

It's all personal preference, this is only a guide on how to fix it if you do not like it.