I've been using Xfinity Home and can give my take on just that.
Pros: Monitored system that will alert a call center, one of my biggest questions is what will I do if I'm not home and the alarm is triggered, this answers that. Offers cameras and as many remote sensors as you want. Comes with its own dedicated touchscreen monitor.
Cons: Three year contract. Cameras are standard definition. Lack of integration into other third party systems. Oh and did I mention you have to sign a three year contract?