It used to be that once you set your Facebook username (URL or vanity URL) that was it. You couldn’t change it. That is no longer the case – Facebook now lets you change it once more, although you do need to go through the process of asking their permission.
I admit I was skeptical as to how easy it would be to do this. I anticipated waiting several days, if not weeks, to hear back from Facebook after an initial request.
Impressive and fast action, especially considering the size of Facebook!
By the way, I also requested two name changes on Facebook Pages too (the name that appears below your cover image) and had similar service/results.