A Few Days ago Facebook launched a commenting feature that allows you to embed videos, photos, or web sites in comments just by including a URL. Your comment will include a video player, a thumbnail of a photo, or a brief overview of the web site being linked to. If you prefer your comment without the preview, you can remove the preview with one click.
Today, Facebook improved the design of the Account Settings page to make editing and updating your account information easier. None of your settings have changed,it just has a new look and feel. Check it out.
Although it looks like Facebook give option to change the username but yet you can not change the username. May be in future you can change the username of your facebook account.