Just played www.live.com a bit. The AJAX benefit is very obvious. No need to have fancy interface, but simple and easy to use.
Finally, I can move out my.netscape.com and my.yahoo.com. Yahoo also have another beta site 360.yahoo.com, but really don't feel any catching -- need to figure out how to fill in the boxes.
This time, MS does much better job than virtual earth. There is still one thing may hold me to use it -- it's hotmail. The hotmail interface and usibility need to catch up. Hotmail need to provide the e-mail address found as typing like yahoo, gmail did.