Compared to other Windows applications, the font rendering in Logos 4 is inferior and - to my eyes - bothersome.
I believe this is due to Logos 4's lack of subpixel rendering. And that is probably due to the terrible implementation of ClearType in WPF. From what if understand, however, WPF 4 has addressed this problem.
I guess, if anything, this is a just FYI for other forum readers since WPF 4 is still in beta. However, I am really looking forward to Logos 4 text becoming more readable as soon as it _is_ released!
Here are some screen shots comparing the same text in Times New Roman in Logos 4 and Word (and zooming in):
Logos 4:

Word:

Logos 4:

Word:

Logos 4:

Word:
