Not sure why by MOSS does not like to change the title of the page you are on. I would think the title would be the logical choice, which is exactly what my customer asked for. Lucky for me MOSS does output the title in a nice, easy to get to location within the page. Just add a Content Editor Web part (which has saved me quite a few times!), mark it as hidden and add the following through the "Source Editor..." button
document.title = document.getElementById('ctl00_PlaceHolderSiteName_onetidProjectPropertyTitle').InnerText;
You may need to do some searching to make sure the element is the same for you.