In Atlanta, not Chicago, but have been a Comcast internet only customer for a couple of years. Used to be a customer of cable as well for 10 years, but cancelled. Honestly, Comcast is an insanely terrible company from a customer service standpoint. Reps don't know anything, lots of hold time, billing issues, etc. I've had several instances where I was speaking to 5+ reps only to get accidentally dropped before issue was resolved. But their internet has been relatively reliable from a service standpoint. Speeds are good and downtime is minimal. My wife works from home half the week so needs a reliable connection and Comcast works well for that. My only other option is AT&T, but their DSL speeds are very slow in comparison and their customer service is just as bad as Comcast.

Only issue I've had with the internet customer service is that once in a while when it does go out, they will do everything possible to blame the equipment or user error. The phone reps will go through the script of checking power, wires, turning on, off, wanting to send you new box and everything. They will never answer the question about whether there is a service outage, the answer is always the service is fine, your equipment must be faulty, we will send a tech out and the charge is $50 for the visit which you have to repeatedly refuse. Even when my neighbors down the street are experiencing outages at the same time, they will not admit to there being an outage. I don't know if there is some sort of metric they have to keep where their service is online 99.99999% or whatever and blaming equipment failure is how they inflate the number. This has happened 3 times now so I've just stopped calling in. It's easier to wait it out, it usually will come back in a short while and dealing with the CS reps doesn't ever help the situation. Fortunately it's not a very common occurrence.