Gmail - The “Attach files” icon changes after the first attachment was uploaded.
OSX Lion - Lets you number your files naturally and shows them in numeric order.
Previously you needed to number them with an appropriate number of preceding zeroes like f.e.: screen 01, screen 02, screen 03.
OS X Lion - When moving multiple files in Mac OS X Lion, an iOS-like bubble shows the number of files being dragged.
/via Hugo Ahlberg
Akismet - When you right click the logo, it shows you a dialogue offering you different high resolution versions of the logo.
Transmit 4 - loading bar indicates both the total transfer and per-file transfer in one progress indicator