The system tray application is very handy; one small improvement could be made with the tooltip - currently the toolltip says "you have X action items", which really just translates to the number of open reviews you are participating in, but doesn't let you know at a glance how many reviews require your attention (see below).
A more useful tooltip would be something like "X open reviews, Y need your attention (Z overdue)", where X would be the number of open reviews you are participating in, Y would be the number of reviews where you are not currently in waiting / approved status, and Z would be the number of reviews that need your attention, and are past the review's configured deadline date.
Correspondingly, it would also be nice if the system tray icon changed to reflect various status, for example a green indicator could indicate 0 reviews requiring your attention, yellow indicating 1+ reviews requiring your attention, and red indicating 1+ reviews requiring your attention that are overdue.