It’s the little things that sometimes impress me the most. Like when this dialog appeared:

…after I’d filled out a form PDF that was emailed to me. It had exactly the option I wanted first and foremost, to send the completed PDF back to the sender.
Sure, manually digging up the completed PDF from disk and dragging it into a Mail Compose [Reply] window isn’t hard, but it just feels so thoughtful when the system saves me the effort. Knowing that someone, somewhere, actually thought through how Mail & Preview might be used, and thought enough of their users to go to the trouble of implementing this.
Kudos to whomever was behind this sweet little feature.