I think the following text would suffice:
"Yo, you dropped some stuff.
Were you fo' real?
[Fo Sho] [Nah dawg]"
Seriously... I think it's most important for XY to stick with a single method and stay consistent in its usage. It's currently OK/Cancel, so unless Don is going to change it everywhere it should remain OK/Cancel. That said, I think Apple has the right idea on button captions in that they should describe what will happen when the user presses them. "Yes" and "OK" are both bad.
I like the header area, while it may be redundant it adds some gloss that improves the aesthetics of the dialog.
Personally I think I'd like to see the dialog eventually become:

- 20101103-142711 - Screenshot.png (12.45 KiB) Viewed 1707 times
And depending on the state of Ctrl/Shift it would automatically default to the correct button, and possibly have one for Backup as well.
However, to keep consistency for the time being I'd make the buttons OK/Cancel and add a line of text to the bottom: "Would you like to move these items?" (Move/Copy, These Items/This Item)