I went through a ton of work to build a feature into an extranet application to allow clicking on a link to open a FOLDER which the end user could drop files into. It would well and was very useful, thus worth the additional pain of forcing IE6 as a requirement.
What does Microsoft do with IE7? BREAK IT!
The username and password were embedded into the URL, for example (not a live one):
Would open a new folder in IE6.. but no more.