I really like the Quick Look feature in Mac OS X Leopard. It is very handy in Mail if someone send you an attachment. For those that never open attachments, this might be a happy medium.
I did notice something strange though when doing a Quick Look with a Microsoft Word document. The arrow cursor changes to text select cursor if you move it over the document, and gives you the impression that you could grab some text to do a cut and paste with it. But no selection seems to take place.
Maybe it is user error but it feels like a bug to me.