Hi simba - the font used by MoI is set under moi.ini, go to Options > General > "Edit .ini file" button. Then inside there the font is set under

[UI]
<....>
UIFontName=Arial

You can set that to a different font to see if a different font works better.

However, it's pretty likely that it's not the font itself that is making things blurry but rather a bug in Wine's font rendering. You will probably have to try a different version of Wine to make the blurriness go away, try the latest development version and see if that helps.

- Michael