I have noticed an issue (unfortunately, I suspect, in the game's engine) that is causing me some grief. If I am moving (be it running, walking, or sneaking), sometimes I will keep moving for a split second instead of stopping when I let go of the movement keys. This is really obvious when I'm sneaking and can be a significant barrier if I am trying to approach something delicately.

I noticed that this only seems to happen if I am moving the mouse at the time I let go of the movement key. If I keep my camera perfectly still, this never happens. If I am moving it, however, I can reproduce this "sliding" really consistently.

Does anyone know what causes this or if there's a workaround? I've seen it suggested that this has been in the engine Bethesda uses since Oblivion, but I really don't remember having this issue when I played FO3, which I played a lot and it is a problem bad enough that I feel like there is no way I would have forgotten about it.

This is an old engine-related bug. It happens, as you have stated, when you are "looking around" when letting go of the movement key.
I think I had this in Oblivion, too, but don't remember seeing it in FO3 (which doesn't say anything, really, likely has been in there as well).

Anyway, I have it in FONV and the only solution I have found is to stop caring about it. This way you may eventually stop noticing... :shrug: