I had written about why I chose Qwest over Comcast and Vonage. Here's how it's going. First off, the Linksys / Cisco box has to be plugged into the cable modem. Fortunately I had set up a telephone wiring block when I set up all the phones in the house. So it took me less than an hour to reroute a dedicated telephone line from the VoiP box to my analogue phones I wanted to use.
Believe it or not, call quality is much better than my landline. I have had no downtime, but then again it's only been a couple of weeks (so keep a landline as one our your lines). The coolest part is I forward all voice mail messages to my gmail account. And my phone gets gmail. So I can quickly check to see if someone has called.
I only had one quality problem when an incoming call came through Google Voice, then to my Qwest VoiP. Usually it works o.k. Have no idea what happened. Next time I'll just call them back directly.
Moral of the story: Don't pay Comcast $40 a month. Get Qwest if you can, or Vonage and save yourself $240 / year. Or look at it this way, if you do that you can take the money saved and get HBO.
update 3 Oct 2010: After 10 months, still works well. Some quality problems occasionally when calling a Google Voice number. Also a couple of weeks ago some idiot at Qwest made their website Internet Explorer only.