I'd argue that you'd still have to install 7z or some program that can deal properly with zip files. While I haven't tried Vista's and 7's implementation, at least XP's was pretty broken. (Stuff like random error messages for proper zip files or files in an archive being silently ignored.)
I have a friend who stopped supporting people who used windows' zip to extract his program because he knew that'd fail. So, please, if you want to continue using that POS, go ahead, but do stop spamming this thread about it...