Would it be possible to update the plugin to allow us to chose WP's short URLs?
This would open up the possibility to use any URL shortener as users can just hook into the WP API rather than having to hack Tweetily.
It would just be a quick change to your core file, an extra option in the service selection drop down, and a call to: wp_get_shortlink();
I'll have a go at hacking in myself but would be great if it could be incorporated. Specifically I use a Yourls plugin to create my WP shortlinks and this simple fix would ensure these links are used.