For a new user to Workrave (or one that missed the changelog that introduced the "Reading Mode"), it would be nice to have some configuration check-box in the "Preferences" wizard that controls the "Reading mode", in addition to the check from the systray menu. As it is now, it is easy to miss this functionality, as a normal user would expect configuration to be in the preferences (yes, it is above "Preferences", but I've simply missed it (-: ).

In my opinion, preferences are used for settings that you don't change very often. 

Reading Mode is a setting that you may change frequently, depending on how you use your computer. Just like the operation mode (quiet, normal, suspend). For this reason, it's in the menu and not in the preferences.