I came back to Comcast HSI after 4 months of being on an AT&T dry loop for DSL. The speed was the same on DSL just without powerboost. The price was cheaper and it was reliable but if you ever need to change or add other services, your screwed. I added home phone service to my DSL service which caused AT&T's system to disconnect me and not be able to restore service. After spending around 6 hours total on and off the phone with AT&T's support reps who in the end told me it would take another 48 hours just to tell me what is wrong, got the boot after I connected my cable modem back into the coax line.
In just 15 minutes a Comcast rep had me up and running with another 6 month promo. Not only on HSI but with TV service as well. I should have never been tempted by price alone. You tend to get what you pay for and I got reminded of that.
8/7/11 Update
Still going strong. Picked up a D3 modem a few months back in which channel bonding was rolled out a few weeks later. A few weeks after that the upstream bonding was removed. Will they get back before the end of the year? (I doubt it)