Tidy Bar reconfigures for your action bars. It retains the design of the standard interface, which reducing the clutter on your screen.
Central Layout: The standard action buttons are centered on the bottom of the screen, with all your additional action buttons stacked above.
Vertical Action Bars: The action bars along the right side of your screen will remain hidden until you hover your mouse over the area.
Bags and Character Buttons: The bag and Character buttons are repositioned to the bottom right corner of your screen, and will remain hidden until you hover your mouse in that area.
Note: A well-known issue occurs when trying to enable or disable an actionbar while in combat; The bars do not reposition themselves until combat has finished. This is unlikely to ever be resolved, being a restriction in Blizzard's UI system; Only Blizzard code may change the position and visibility of a secure frame during combat.
The stupid rested-state bar isn't positioning itself properly. I haven't had a chance to figure out a fix.