It's great for all those users who are not still used to the torrent filesharing system.
You only have to drag and drop the torrent file in the interface of the program and the download will start automatically. If you keep the file over the interface for a while, you'll see the title of the file you are about to download.
Transmission also offers advanced configuration settings that will delight all those advanced users who like changing settings: limit bandwidth, view files, share only certain folders, etc.
For Mac OS 10.4.11 or higher, Leopard included. Mac OS X Panther (10.3.9), please download Transmission 0.6.1;