Dude,
This is a renewal EAD, not a new EAD; so the date of the RE-NWED card will start from the date of the expiray of the existing card. So you will not be loosing any time. I have done this three times already and never lost a day. Unless they have changed the system, which I doubt it.
I have already submitted my application (through the lawyer), and have a receipt for the application submission.
I am not sure how to apply in person. May be wimbeldon, or nice'n patient can shed some light. To the best of my understanding, the application by mail is easier than going over there to the office.
My understanding about the on-line submission is that it is not any faster. But it may be the way to go for you. It is not a problem at all, but it is not going to be any faster. I have not tried it anyway.
I hope this help clarifying the points you were asking about.
Cheers,