Modest performance improvements
Based on Adobe's preliminary testing, the 64-bit version of Photoshop CS4 will give a performance kick of about 8 percent to 12 percent compared with the 32-bit version, Nack said. For one particular task--opening up a huge 3.2-gigapixel file on a system with a lot of memory--the 64-bit version is 10 times faster because it doesn't have to write the data that won't fit in memory onto a relatively slow hard drive.
In practice, a huge swath of Photoshop users won't be affected by the difference, at least initially. The transition from 32-bit to 64-bit computing has been creeping sluggishly across the personal-computing industry for years already, and it's going to be some more years before the transition is complete.