Currently only Login using username seems to be allowed, I would really like to see login using email ID be allowed too. it's pretty standard to see login using email being allowed, and it really doesn't take much, I know from experience.
I just registered, and when I realised I needed my username to login, I kinda panicked, cause I had half forgotten it(I've seriously not needed to remember usernames since 2007). I use my email, which is easy to remember, to login to almost everything except IRC.