If it wasn't for my wife and kids, I'd ditch comcast as well. The other problem is I've got the 3 service bundle: ISP, phone, TV cable
I think the whole package is around $180/month (we negotiated it down). To just cut the cable and return the monthly DVR box we rent would only save $60 or so.
We've considered tossing the landline, but we do have a monitored alarm/security system hardwired (another monthly expense).
Also, with my wife and I on the same mobile carrier, there's no phone redundancy if that service was interrupted should we rely exclusively on cell towers.