Perhaps I missed it, because there's plenty of documentation, which is great of course, but I somehow felt a bit overwhelmed with detail so couldn't really see the wood for the trees.
EDIT: a few key differences as far as I could spot (although not sure what's the most fundamental difference):
* plugins can be dynamically loaded (e.g. from a git url), even via the chat interface itself.
* more focus on security / permissions to administer (I'm guessing that's also partially connected to the dynamic nature of plugins, because without security it's very easy to mess things up)
* plugin eco-system seems a bit thin(?) could only find a strange list to github repos
* built-in per-plugin persistence (not sure how it is actually stored though)
(It seems to be a bit late to be doing IRC bots. Can you do 'bots on Kik?)
Here's an example of one of the more intricate modules we've open sourced:
"ChatOps: Technology and Philosophy"