Do You Want to Kill the Surprise?
One of the most difficult things about any branding project is telling people "No." As in, "No, you can't use the new logo version in the old template," "No, you can't use the new slogan for a white paper you're sending out," or "No, you can't place the new logo into your email signature files."
Your answer is usually not, "No" but "Not Yet." That's because as excitement and enthusiasm runs high for a branding project that has been in the works for a number of weeks, people involved with the project naturally want to begin publicizing the fruits of their labor.
Unfortunately, as the brand police, it's our job to keep a lid on publicity until we're ready to launch the brand. And then--rip the covers off, go nuts, use your new branding all over. Just make sure to follow the style guide.