I posted in an existing topic that's furthermore been marked as solved.
maybe that wasn't very smart, so here the question again, for all the helpful people out there to read easily.

The mouselook behaves weird. There's probably some delay about it or it accelerates while moving the mouse. In any case it makes the game hard to play- without getting used to it, that is.
Is there a way to solve the problem? I already checked the ini-files for interesting values, but couldn't find any (except for sensitivity).
Any ideas?

Thanks.

I had the same problem. I installed the unofficial patch at the the following address at the mouse look is improved a lot but still feels a little strange

http://www.oldunreal.com/downloads.html

Seeing as I just installed the patch, I can't say much more than so far mouse look is much better than it was than in the vanilla install, you might want to give it a shot yourself.

After installing the patch, open the game using OpenGL, check mouse look smoothing and max mouse look smoothing in the in game options menu and see it it works better for you. One thing I noticed is sometimes the screen slowly looks down as if someone is slowly dragging the mouse in that direction. Saving the game and reloading right after fixes it.

Hope it works for you

This patch did a great job. Many thanks dude!