I have Comcast's HD DVR -- it's okay, but not nearly as good as Tivo. If you can get an HD Tivo at anywhere near the same price, I'd go Tivo in a heartbeat.
I got DVR for the world cup back in 06' and have had it ever since. Once you start using it, it's hard to imagine having TV without it. You can't jump by time, but the fast forward and rewind feature is very quick. That's risky dropping $120 on something that you don't know will even work. I'd just go through comcast.
I just renegotiated my Comcast deal yesterday. I threaten to go to Qwest/DirectTV every time they try to up my rate. They kept my "teaser rate" of $4.99/mo on the DVR box. You can negotiate that rate too. Just threaten to leave or threaten to reduce your number of channels because the box is too expensive.
Why don't you give it a try for a month or two? it's not a contract thing with the dvr. Of course if you try it out, it'll be hard to get rid of it.
FYI for those of you with a Comcast DVR box and want to program a button to jump 30 seconds. Since most commercials are 30 seconds, it works much faster than fast forwarding. Choose an unused or unneeded button on the “silver” remote to be the 30-second skip command. I used my “A-lock” button since I never use it. Other choices are the PIP buttons at the bottom, (maybe there’s a hack for those too?) or the “help” button (there’s no help either). Press the “Cable” button at the top of the remote to put it into Cable Box control mode. Press and hold the “Setup” button until the “Cable” button blinks twice. Type in the code 994. The “Cable” button will blink twice. Press (do not hold) the “Setup” button. Type in the code 00173. Press whatever button you want to map the 30-second skip command to.
Can't you just have Dick Vardanega handle it for you? He could probably get a better deal than I ever could.