Chirrup is a bit different -- looks like more of a programmable API than something for end users.
Chirrup fetches all of the replies from Twitter,
and sorts them by URL so you can have a comment feed
for each page in your site.
This is actually not very much our new feature at all, since Chirrup is a feed service (pull from Twitter by API) whereas ours is a way to post comments to Twitter at user's choice (push to Twitter by user)
However, it is quite a bit like Backtype.com's new Backtype Connect, which tracks not just Twitter but comments from other all other kinds of blogs (Wordpress, Typepad, Six Apart), Reddit, Digg, Hacker News. And even Posterous. =)
Here's Backtype's recent blog post just the other day about Backtype Connect API, which is fully programmable.
Chirrup was designed as a way to mediate your blog comments (or comments anywhere really) through Twitter. Since it does take the discussion to twitter, Angryamoeba's goal was to follow the rest of the conversational thread on twitter, and keep that updated on the blog post as well.
Cool stuff. I love using posterous, pretty much covers everything I need.
The only thing that stands out might be a slightly nicer post-editing experience online, but I only have to edit posts every once and awhile. The email optimization is beautifully executed.
Garry, how quickly do you release new features? I think I suggested one-every-five-days before, but I was being facetious. Either way, you guys have added more features every month than most sites I use do all year.
On my own blog, I almost went so far as to offload all comments to twitter. Basically, each blog entry would have a corresponding tweet that you would @reply to. But then I concluded that most people don't want their comments on blogs filling their twitter stream.
Angryamoeba has been doing this for months now :)
Although unfortunately this was prior to the OAuth api being released. People are using it though, and an OAuth version is in the works.
Of course the other nice thing about Chirrup, is that you don't have to use Posterous to get this capability. :D