I've used Comcast for 6 years and I have had more good experiences than bad with them. However, the bad were so ridiculous it's hard to believe they happened. A few months back, they disconnected HD services for everyone using a specific model cable box (which they had rented to us), and made people call in to restore their HD service because apparently some customers with that box were getting better service than they paid for. What kind of idiotic company policy is that? Disconnect service for EVERYONE? How absurd is that?
Apart from that, I haven't found that Comcast deserves all the negative feelings that people have towards them. I've had worse experiences with Qwest and Verizon than with Comcast.