Previously, you could remove Apple's Helvetica fonts and permanently use Type 1 PostScript versions in their place. Not any more. Address Book is one app which will not launch if Apple's version of Helvetica is missing. So for prepress, designers or others who must use Type 1 PostScript versions of Helvetica or Helvetica Neue, it is now a requirement to copy Apple's Helvetica fonts to a non Fonts folder location, remove them from the System and ProtectedFonts folders, and then set up separate sets in your font manager for Apple's Helvetica fonts, and another for your third party Helvetica fonts. Then turn on whichever set you need at the time and turn the other set off. It's not perfect as you may need the the Type 1 fonts open, which will leave you temporarily unable to open Address Book until you disable the Type 1 fonts and turn the Apple supplied versions on. But there is no way around it. You simply can't have both on at the same time. The main thing to be aware of under Lion is that when you disable Apple's Helvetica and Helvetica Neue fonts, you are disabling quite a few fonts. Which consist of:
Helvetica, Helvetica Bold, Helvetica Oblique, Helvetica BoldOblique, Helvetica Light, Helvetica LightOblique, Helvetica Neue, Helvetica Neue Bold, Helvetica Neue Italic, Helvetica Neue Bold Italic, Helvetica Neue Bold Condensed, Helvetica Neue UltraLight, Helvetica Neue UltraLight Italic, Helvetica Neue Light, Helvetica Neue Light Italic, Helvetica Neue Black Condensed, Helvetica Neue Medium