I use Comcast for my primary business internet connection. In addition to Comcast, I have an AT&T DSL backup connection. I run my phones on a PRI; the T1 for this is provided by AT&T. Of all my local services, telephone is the most critical (I of course host my web sites off site at a data center).
Comcast regularly calls my business trying to sell phone service. They have great rates on phone service, but they do not offer guaranteed up time according to the reps.
Memphis had a serious wind storm the evening of April 19, 2011 (Tuesday). You can see what it did in my area in one of my earlier posts.
I'm glad I don't use Comcast for phones because I would not have phones right now with Comcast. It's that simple! Several businesses in my building use Comcast's phone service, and they have effectively been out of business since yesterday morning. I pay more with my current method of phone service, but I am ALWAYS up. In the event of an outage, AT&T guarantees a work crew will start fixing my system within 4 hours.