Whether Google actually handles 302s properly is an open question. If a 302 is used instead of a 301, search engines might continue to index the old URL, and disregard the new one as a duplicate. Link popularity might be divided between the two urls, hurting search rankings. Search engines might figure out how to handle the 302, or they might not. Google spokespeople have said that they will treat a 302 as a 301 if they think the webmaster has made an error, but why take a chance, and what about other search engines?