Just got upstream channel bonding today (02-06-2012) in Springfield, MA. I upgraded to Extreme 50 a couple of months ago but I had to post in the direct forum because I was not getting the Extreme 50 speeds. After they pushed the Extreme 50 configuration file, I got upstream channel bonding.
It appears that only the customers on the higher tiers (50 and 105) get the upstream channel bonding. -- All of my CPE (including my EMTA) is customer owned. The only Comcast owned equipment in my house is the CableCards in the two TiVO boxes I own.
Only channel on the 50 meg tier? Is that really true? I don't know bout that
It depends on the CMTS in use in your area. On an Arris C4 CMTS (which I understand is the most common) every tier will recieve bonding -- but other CMTSes may be configured to only enable bonding for those on Extreme tiers.