I got a phone call from Comcast last night. A recorded message told me that the service would be briefly down for upgrades in the early hours, and that the result would be double internet speeds for "most" customers at no extra cost.
My speed seems to have got a nice bump: throughput from about 15 mbps to 28 mbps. (Update: just checked to see what I'm paying for: 16mbps.) However, it's not consistent
I'm on the northside, near the Heinz Lofts and the Penn Brewery. I tested with Comcast's own test applet.
Do tell us if Comcast doesn't double your internet speed for free, Pittsburgh.