The Official Microsoft Windows 8 blog has given details about the re-designed experience for managing file collisions in the Choose Files dialog box.

In the implemented design, there are two levels of control when acting on file name collisions (or “conflicts”).
•The primary experience is a simplified, one-click, bulk management of all conflicts, offering “Replace all” or “Skip all.” We call this the “Simple Conflict Resolution dialog.”
•There is also an option to enter the secondary experience which offers more information and more fine-grained control. This is the “Detailed Conflict Resolution dialog.”

Go here for a full read.