I recently installed Tweetable, version 1.1.4, which is tested through WP 2.8.1.
Everything went off without a hitch, except that it will not post new tweets when I create a new blog post. I ran over the code for a little bit and couldn't figure out where/how the auto-tweets were binding to new posts. Granted, I'm a novice WP user, so I may just be missing a concept or two that precludes me from figuring this out on my own. In any case, I'm a part-time PHP developer, so can understand (at least) most of whatever response I got.
Thanks in advance!
Edit: I searched each file for "update_status" - to no avail - since it was referenced in one of the support posts. This makes me wonder if I'm just missing a file altogether. For what it's worth, I added the plugin through WP.