Personally, I feel like a confirmation for any form field is insulting. Is it there to prevent typos? I can almost understand it for the password as it's obfuscated by dots (hence harder to see if you made a mistake), but I can "feel" when typos happen, and if one happens when entering my password for the first time I'll just clear the field and type it again.

In the case that I accidentally register with a typo-ed password, I'll just reset it through my email (which I never mistype via. Typinator). Alternatively, the password probably got saved by Chrome.

If anything, I'd remove the Username field and just make the email address the username (assuming the backend could gracefully handle the transition). My chances of registering go up exponentially the smaller the form gets, which - I would postulate - is the primary reason the "log in with facebook/github/open id" buttons are so effective.