I was there when MSN 6.0 was shuffled for beta testing.Me and one of my friend from Microsft messanger team was having fun of chatting with Beta version after 2 week they launched the site with full promotios.
Since I am a microsoft fan even though they had to give up $6million recently, I strongly belived that PC is easily approachable to human being because of Bill.
MSN is having lot of features like background, emotions, change the display name and most important make you offline and still received the email.
Some eature they are missing is invisible, sometimes people want to invisible and chat only with those whom they want to.I hope MS is working on this and you will get that in very soon.
Second feature what people really wanted to use the diplay pictures for different people fro eg When A is talking to B he wants to show pic xx and to C pic yy, it would be fun for those who has one girl friend and trying to get a new one with a cool pic..just kidding
Also you can download and images from different web site and add on the back ground, emotions, dispaly.
Overall its recommended to use MSN messaneger.