With the upcoming WordPress 2.9 release and the new version of the WordPress.com stats plugin for self-hosted blogs the choice shorturl generator to use has become easier for most users.
The wp.me shorturls domain was introduced earlier this year for WordPress.com hosted blogs. As of Release Candidate 1 for WordPress 2.9 the URL shortener is now also available for your self-hosted blogs.
As soon as you have entered a title for a new entry the Get Shortlink button will become visible and give you a WP.me URL for your entry.
There are no stats available for the shorturl itself, but it will be a surprise if this option will not be implemented in the future.