Holding down the option key while selecting the Action menu will change many of the items which normally apply to just selected files to instead apply to the whole repository. Eg., the menu item "Commit Selected Files..." will become "Commit All Files..."
In many of the dialogs if you hold down the command key (⌘), the buttons in the dialog will display an equivalent command key you can use from the keyboard instead of clicking the button with your mouse.
Near the bottom of the commit dialog box there are two tables. You can interact with each of these tables as follows:
In the left hand table is the list of files which are part of this commit. Double clicking on a file will show the differences between this file and its parent revision.
In the right hand table is the list of previous commit messages. Double clicking on a previous message will insert the text of this message at the current insertion point in the commit message.
Many of the views provide contextual menus. Thus you can right click in the view and see a menu of actions which are specific to the view you clicked on. Views that include contextual menu support are:
You can use drag and drop in:
The Repository List (sidebar) to drag repositories in from the OSX Finder.
The Repository List (sidebar) to reorder repositories in the sidebar.
The Import Patches Sheet. You can add patches by directly dragging the patch files in from the OSX Finder.