I use Yahoo, MSN and AIM
-Yahoo has the best features, but doenst have a "catchy look" to it's instant messaging program
-MSN Messanger is a catch to the eye, but they still need to work out features and do less "brower-based" ideas
-AIM has good features, but not as powerful as Yahoo, and it has good looks also but still doesnt give an eyes glance like MSN does. A good charactoristic for AIM is it's alert features, and its "buddy list" options (e.g. "warning people" and being able to talk to people NOT on your buddy list).
I mainly use MSN because everyone else has/uses MSN also, I think less-advances people use it because it is so easy to install and mess around with, otherwise if not that I would go with Yahoo! Messanger and then AIM
My ranks of use would be...
1) MSN
2) Yahoo!
3) AIM
As far as features...
1) Yahoo!
2) AIM
3) MSN
Styles..
1) MSN
2) AIM
3) Yahoo!
Overall I would give MSN the best rating because they are slightly improving over time and might eventually catch up to the features all the others have. One thing that sucks about MSN is that you can only have up to 150, I think they should up it to 1000, or go by your computers specifications (e.g. if your computer is old/slow it would standardly put 150 for max, or if you have a fast computer 1000 would be max because you would be able to handle X amount of people all signing on at the same/or around the same time). Or they could just have there be no limit...