Use Cases and Deployment Scope
Bitly is one of the early URL shortener programs. I like being able to track all clicks over a limitless timeframe. I can always go to my Bitly dashboard and see the results of my shared URLs from AD campaigns, FB posts, and other content streams I push to.
Bitly is easy to use. The URL for seeing the metrics over time is also simply adding /# to the bit.ly link and there is your data.
I have created so many bit.ly links over time that I occasionally run into "unique" URL names conflicting with links I had already created.
Bitly is fast, complete, and provides excellent back-end reporting.