Users of localized versions might need to use the english version for several reasons: following one of the many english tutorials on the web, using some of the shortcuts that are not available in other languages, use some actions that have been written in english without making sure they would not break in other languages.
Some countries have multiple national languages, and companies might have employees speaking different languages using the same machine. Letting them select their language of choice would be a must!
The only legal way to do it now seems to purchase another version of the software en english, install it, then use the preferences entry to change the languages.
But paying a whole new license of Photoshop is quite expensive, especially if one knows that other software, also produced by Adobe, allow their users to change the langage of their interface for free: After Effects, Lightroom, Bridge are examples I know of.
After effects users can switch their localized version to english in order to use english-written expressions, or to follow the vast amount of tutorials in english: (it's even evangelized as a useful function!: http://blogs.adobe.com/toddkopriva/20... )
Lightroom follows the language of the Operating System, at least on Macintosh.
Bridge allows the change of its UI Language in its preferences.
Please empower your users! Some multi-lingual users would then be able to evangelize in multiple languages, therefore helping and reaching more customers, and giving them more incentives to purchase (because they know they would get help...)