Rated 4 out of 5 stars

Works fine on TB5 if you install the Add-on Compatibility Reporter (Add-on Compatibility Reporter).
I would like to tweak the colors though, they don't match what I am used to in Outlook 2007.

This review is for a previous version of the add-on (2.2). 

Version 5.0 allows customization of colors

Calendar Tweaks 5.0 allows user customization of 'Today' and 'Selected Day' colors (header background color, day box background color, and border color).