When we were at the Comcast office just recently we were told that they had no idea when the switch would take place, but most likely sometime this summer. Guess September is still summer technically...
We had all digital with Cox and honestly, with high def tv's, I couldn't tell the difference.
Ordering the boxes needed online is wise. One can call and order them or pick them up at the office, but I'd recommend only going to the office if you have other things to take care of with Comcast....office is VERY busy!