I think he is done and I think he is guilty of the allegations. Fair or not, I have had it with pro athletes of all sports with PEDs. I am too tired of a star having some strong statement against them and then testing positive (marion jones, Raffy Palmero, etc). Fans are way too quick to believe their hero's and accept insane excuses.
Many will say it is not fair, but I (and many others) have taken the guilty until proven otherwise approach to this issue. There is too much money and too much fame on the line and people will do anything to win. It is, at the same time, what makes top athletes amazing and makes many cheat - the win at all costs mindset.