Another advantage is that you can use the old keyboard shortcut for sharing items: Shift+S. Unfortunately, you can't use keyboard shortcuts in the modal dialog, so you still need to click "Share".
Decoupling the "+1" button from the "share" button is a good idea and Google should adjust the code of the +1 widget to make this possible. "Liking" and "sharing" are two different actions and should be treated separately, especially considering that +1's are always public, while sharing can be limited to a few people or circles.
{ Thanks, Zachary and Herin. }