There havent been any good ones..
The one on Plurk.com made me roll my eyes. They could have come up with something better than that "Bitter" post about changing their entire platform.
We have decided to call this wonderful new service of ours Bitter. Here is how it will differ from Plurk:
* No more emoticons. No fun.
* Forced usage of geeky conventions such as “@username” and “#blah”.
* You will be unable to follow conversation replies easily.
* No more picture or video embeds. Life in mono rocks!
* Promoting a landfill of unmarked, potentially incentivized and potentially misleading url shortened links.
* No more private messages to a smaller subset or clique of your friends or followers.
* Limited customization options aimed at keeping the tone of the service clinical, boring, spammy and lifeless.