Pre-orders and previews begin April 10, launches April 24.
Mac OS X Leopard Retail Box Video (Hologram)
As it turns out, Apple has stepped it up with the Leopard retail box as this YouTube video shows. Leopard appears to come in a small DVD-sized box, with a large "X" on the front. The "X" appears to float above the Leopard desktop photo and has a holographic effect when you move the box back and forth.
Mac OS X Leopard will be launching on Friday, October 26th at 6 p.m.
Update: Stills of the Leopard Box have also been posted to Flickr: Front, Back, DVD