Comparison of free Instant Messaging clients

amsn

 ms windows live messenger clone with most features (including video conference)

heavy in memory (60+ MB)

unstable (e.g. didn't login in first run => unstable state => needed to restart)

pidgin

simple but clean interface

smooth scrolling in chat window

tabs for each conversation in chat window

aspell is heavy in memory (100+ MB) => 20 MB without aspell

problem with emoticon: no size limit => huge pictures!