3 * Better code sharing. For example, don't have to duplicate tab layout or bookmark bar layout code.
6 * All the animationy bits
7 * Subtle click selection behavior (curved corners)
8 * Drag behavior, including dropping of files onto the URL bar
11 * drag & drop behavior, including menus
13 * Easier for folks to work on both platforms without knowing much about the underlying toolkits.
14 * Don't have to implement ui features twice.
20 * Font size changes (e.g., changing the system font size will apply to our dialogs)
21 * Better RTL (e.g., http://crbug.com/2822 http://crbug.com/5729 http://crbug.com/6082 http://crbug.com/6103 http://crbug.com/6125 http://crbug.com/8686 http://crbug.com/8649 )
22 * Being able to obey the user's system theme
23 * Accessibility for buttons and dialogs (but not for tabstrip and bookmarks)
24 * A better change at good remote X performance?
25 * We still would currently need Pango / Cairo for text layout, so it will be more efficient to just draw that during the Gtk pipeline instead of with Skia.
26 * Gtk widgets will automatically "feel and behave" like Linux. The behavior of our own Views system does not necessarily feel right on Linux.
27 * People working on Windows features don't need to worry about breaking the Linux build.