So if you need a prior release, what do you do? The challenge is, once a new release comes out, Adobe no longer officially sells the older version ( with one exception). And occasionally some folks say they prefer the earlier, simpler versions over newer ones with more features. Two common reasons are the higher system requirements – 64-bit for some components of CS5 like After Effects & Premiere Pro, as well as cases where the rest of a customer’s site is still running an older version and would like to add a new setup with the same compatibility.
Adobe’s Creative Suite 5.5 has been out since May, and has generally been well-reviewed and even lauded as a must-have release… Nevertheless, some folks are still looking for or require older versions of the software, like CS5.0 or CS4.