A Google Webmaster Help thread has a discussion around using redirects. Typically, you should always use a 301, permanent, redirect when you are redirecting a page to another page. But Googler, JohnMu, said there is one occasion where it is preferred to use a temporary, 302 redirect.
When is it preferred to use a 302 redirect? John said:
A 302 redirect is the correct redirect from a root URL to a detail page (such as from "/" to "/sites/bursa/"). This is one of the few situations where a 302 redirect is preferred over a 301 redirect.
But he does add that when possible, try to avoid the redirect all together and show the detailed content on the main root URL. John added, "if you were hosting this yourself, you might want to look into saving an additional jump by just serving the content directly (it's not necessary, but if you can do it, it's always nice to save the user a redirect)."
Forum discussion at Google Webmaster Help.
