Thanks to everyone for their suggestions!
Setting Filter Quality to Low improves the font rendering considerably. Not perfect now but still...
Now I only need it to run in fullscreen mode. ALT+Enter doesn't help. There are no corresponding options in the video settings, and I couldn't find a command line switch. I did reinstall and quickly test Dom2 just to rule out faulty driver installations etc.
Oh well, life's a ... witch and then you die
