It works wonderfully, except there is no way to track how many people click your shortened urls because you're not logged into your tr.im account when the urls are shortened. There is a crazy easy way to log in to your tr.im account when TextExpander shortens your urls.
Add this script as a new TextEpxander snippet. Fill in your username and password where it says
Set the shortcut to something like "trm" or similar.
Thats it! Anytime you want to shorten a url in any application, copy the url to the clipboard. Next go to where you'd like to paste the url. Type in "trm" or your shortcut, and it will paste the shortened url automatically, and the url's click stats will be available in your Tr.im profile.