I registered an account yesterday by entering my info and a username and everything worked. I login with my username and password.
Today I show my friend v2 and he installs it and now when he registers it asks only for email and password. He can login on the phone, but on v2.airdroid.com it asks for a username and password and no matter what it always says "The username is incorrect".

So it is unusable. Oh and the first time he must have hit a wrong key when creating his password because he couldn't login on the phone. I would love to talk to the individuals who thought that they would go against over a decade of common sense and only ask for a new password only once on notoriously troublesome phone touch keyboards.