"our Intranet pages were coded to work with IE6"... it's this kind of stupidity that is the cause behind so many of the problems in web pages / services these days.

Other than this, the "intranet" option is likely to be their work around to allow sharepointless to actually work... in the latest version MS purposefully reduced functionality for anything other than IE (and all in the name of compatibility). Doubtless if IE8 worked in any forms of standards, sharepoint would fail. The problem is, sharepoint is so pathalogically badly designed and cobbled together that there's no way they could fix it and maintain any form of compatibility between "applications" designed for older versions of it and a newer version. Instead, MS can only add more and more bloat (occasionally touted as features) and make an already awful system even slower and less efficient than previously.