Developers can start using OS X Lion from today, but the rest of us will have to wait until summer to start using the iPad/Mac OS hybrid—which includes a neat new way to share files over the same Wi-Fi connection.
Through the new AirDrop icon, located in the Finder sidebar, users of the updated operating system will be able to drag and drop files to a contact's name. That file will show up in their Downloads folder, which they can then access instantly. Once AirDrop is closed, the connection between the computers will also close.
Unfortunately it seems to only be between OS X Lion users, and not between Lion and iOS—but give them time, I'm sure.