This is the killer feature in Windows 7 as far as I'm concerned. This and the searchable Start Menu.
It's simple, but I use it dozens of times a day. It's quick. It's effective. It's listed in the title of this blog post, completely undermining any attempted suspense. It is, of course, the wonder of ICT Tip 037 - Aero Snap.doc!
A lot of people have no idea that this exists, despite it being useful for nearly everyone. Send it out. Tell them. Share the joy of knowledge. Just