Dave, the problem with ad_returnredirect is that whenever a user comes to the site with IE 5+, they get the ugly util_ReturnMetaRefresh hack. You can write a new version of it to give the user a templated page that looks like the rest of the site, but still. It's ugly. And nearly all users of OACS sites are using IE these days, eh?
I see that util_ReturnMetaRefresh is deprecated in HEAD. Is there a better solution to the problem of IE not handling multipart/form-data correctly? If so, what is it?