TPG - Super Fast Standard 75GB For $50 - Upgrade For Free. Updated 4/09/09 it is 80GB for $50 now.
I just found about this this morning. It seem like if you are already on $50 55GB super fast standard plan , you now can upgrade to 75GB plan for free. There are also other changes to the other plan too. Check it out on the TPG website.
All you need to do is log in your account and change your plan. I think it wont reset your plan.