It's the same as is but smaller with one big fan rather than 2, it now has an internal hard drive that is removable and NO the old hard drive will not be compatible. WIFI. Oh and a port for KINECT so you don't need extra power supply.

For those that aint seen the unboxing of the new XBOX 360S follow this link and see what it has to offer and YES I am buying one www.engadget.com/2010/06/14/xbox-360-250gb-first-unboxing/