Check out Google Talk. New messenger client from Google. I installed it today.

First thing what you notice is its installer size. Its very small and will install very fast even in slower internet connections.
User Interface feels bit clumsy as of now, but Im sure its going to be a better with versions to come.
Phone call qulity seems to be better that that of Yahoo.
Only bad thing is..no emoicons!!! Lets wait and watch and see what google has in the box.....