Some new information about Apple's Rosetta technology has been posted at CNET. Rosetta is an emulation technology provided by Transitive, to run PowerPC applications on x86 processors.
As a program runs, Rosetta translates its PowerPC instructions into corresponding x86 instructions. Although there are limits to what programs it can translate, the software promises to ease the transition that current Apple customers and software developers face. Apple Chief Executive Steve Jobs on Monday demonstrated Rosetta during a keynote address, showing it running PowerPC versions of Adobe Photoshop and Microsoft Word and Excel--three applications essential to the success of the Macintosh line.
More details about the performance of Rosetta can be read at CNET