After quite some time with the docs and google (and help on IRC from some a nice guy named Sidnicious) I finally made my app behave as it should, and now it shortens the URLs you drop on it (as was requested by one of my very few users).
UPD: It now has Growl integration! Hooray!
You can grab the new version here
Seems the last thing to do is to add some configuration (api key for instance).