Pros
Comcast was an interesting place to work, as a developer it really tests your ability to balance latest technology with legacy systems. There are always a ton of jobs open, so if you wanted to move to a different area or job altogether you could. Transfer requests were handled (for the most part) with dignity and grace. Overall a good work experience if you don't mind working for a slow moving behemoth. Working at Comcast gives you an inside look on how a massive corporation functions at a high level, sadly more often than not the answer is that it doesn't function well at all.
Kontras
The pay when i worked there was horrible, so bad in fact when i took a new job i was moving up ~75% in salary while maintaining the same job title. Raises were a capped % (5 i think was max for a top performer) which is insulting. Alot of the people are terribly inept at their job, and to help cover the fact they dont' know what they're doing; they tend to slow down every project that comes their way into cancellation. Comcast is an example of an old style company trying to make it in a new world.