I would agree with Masaki and make sure you are covered for 911, in our case we have Vonage for about a year, that was a disaster. For months when we lost power a couple of times we had no phone, also we have a alarm system in our house and the couple of times it triggered, we later found the alarm company was not being called because the alarm was dialing on a dead line.
We have Comcast highspeed internet/Phone/Cable with 2DVR boxes and and extra fax line, its a little pricey at $180.00 per month, but the service is fantastic, and Comcast now has Powerboost for a faster internet.

Frank