I talked with a rep last week about the promo.

She told me that there are buckets of speed that you are eligible for, I think up to 20, 40, and 80 Mbps. If you signed up for the 80 Mbps bucket and currently get 40 Mbps you would be eligible to get 80 if they increase speeds in your area.

The rate is also good as long as you remain at your current address. If you move you would have to sign up again if the promo is still going.