i’ve written a guest post at read/writeweb exploring the ui advantage that plurk has over other microblogging sites.
if you think about the basic functionality, all micro-blogging sites offer more or less the same. you can create an account, add some friends, and then message back and forth (privately and publicly) and share stuff with each other. what plurk does differently is the user interface and the effect of this change reverberates throughout the site. here are the major ui changes and their impact.