At ChessyCam, they have posted a couple of videos, the first one shot using the 3x zoom. They note that things "get a bit soft" at 10x. ChessyCam: T3i 3x Zoom w/ 100mm F/2.8L IS Macro
A second clip from ChessyCam shows both 3x and 10x zoom on a dime.
Canon T3i / 600D Macro Test with 3x-10x Zoom Feature from emmagination on Vimeo.
Amazon has the Canon T3i in stock and shipping: