i am new to this group...
i am also working with same types of issue...
i think there is also one major difference b/w window.popup and other Divs or windo.open
window.popup , gives a popup which can be on top of any windowed elements like (<select> i.e). which is not possible by any other alternatives. this is very much required when creating DHTML navigation bar.
also , i have tried http://msdn.microsoft.com/workshop/samples/author/dhtml/popup/usingpopup.htm
in firefox, no feature is working,, that's why ,i am also searching some thing excatly like window.oppuo for firefox and netscape browsers..
if some body have any suggestions, please let me know..