Yes, I can confirm that you need at least 25 Page "likes" to get a custom (vanity) url. You can also get a custom url for your own personal profile, for anyone who is interested. I would post the link, but I apparently can't do that yet, so I would say to go to FB knowledge base and do a search for "profile url fanpage" (no need for the quotes when you search). I hope that that helps.
wow, learned something today about facebook. That username feature is very cool and saves lot of keystrokes for lot people. http://www.WebDirectory.CO/
If you want short url for SMO purpose then you can use goo.gl (Google url shortner), bitly.com, tiny url. but if want your facebook fanpage username then you will have to 25 likes on your page and then use facebook.com/username from where you can easily get short url.