After an hour on the phone with Comcast, it's pretty clear that their conversion to digital obsoletes my TiVo Series 2 DT and my Panasonic ReplayTV - I can't find any answers in my search of this forum or the TiVo web site forum (of course, I may not know what terms to search for).
Hmmm... "obsoletes"? No. I hope I can help, at least a little.
First, I don't have a S2DT, but my understanding is that the conversion to "all-digital" for cable networks simply changes your S2DT into a regular S2, in terms of capabilities. I haven't had to deal with it, here, yet (it is due on October 20), but my understanding is that on that day, I'll have acquired from Comcast a DTA, which I'll hook into my S2 (and I believe there is a way for you to do so with your S2DT, as well), and connect back up the IR emitters that came with the S2 (again, I'm assuming that they came with the S2DT as well, or at least the S2DT supports them, but you may have to purchase them), and then I'll have to configure my S2 to drive channel changes in the DTA via the IR emitters.
I had this all set up this way, before I bought my S3. So I have little doubt that I can set it up again.
Sorry: I cannot even begin to help you with the ReplayTV box.
I've been humming along (somewhat) in ignorant bliss listening to the TV ads for the past year that if I'm a Comcast customer, I don't have to do anything when everyone switches to digital. That was a big lie!
Not at all. The broadcast transition to digital occurred on June 12. No Comcast customer needed to do anything whatsoever in response to the transition. Nada.
What you're seeing now is a completely different digital transition, prompted mostly by the very vigorous competition in the cable/satellite television market. Figure that almost all of your other options: Dish Network, DirecTV, IPTV suppliers like FiOS, etc., all
already require you to have a box on every television you wish to tune in cable networks. If anything (and folks are very quick to make this assertion...) Comcast is way behind and playing catch-up. They'll finally catch-up, here, on October 20.
It kind-of sucks for those of us who have a lot invested (not just money, but time and effort getting things set up just the way that works best for us) in older technology. I've already begun adjusting... by purchasing a TiVo Series 3 a few years ago. I used to have two S2s and an S1. One S2 is now gathering dust in my basement. The S1 is still running, but simply records The Weather Channel in the 30 minute playback buffer 24/7, so at any time we can rewind and get the latest weather. (Heck, at least it isn't doing nothing eh?

) However, I do recognize that come October 20, I do need to adjust a little bit more.
I could, I suppose, replace my S2 with a new TiVo HD, but $550 is a bit too steep for a box that we only really use to record a few shows each week, and watch typically only while eating dinner. You, though -- you don't have a digital DVR yet and, if you're anything like me, that's going to be a major hindrance for you until you get one, since time will march on, and more and more you're going to find that what you want will require getting a digital DVR.
I'm leaning toward switching to satellite
Neither DirecTV nor Dish Network will allow you to use the tuner in your S2DT. You'll be no better off, in this regard, with a satellite provider than you'll be with Comcast. You've really been lucky, given your situation and needs, that Comcast has been stalling with regard to this... as I mentioned before, all the competitors that you could possibly consider
already have made the switch that Comcast is making in your area.
If anyone has a solution that I can inexpensively implement, and doesn't require and engineering degree, I would really appreciate it.
I'll be glad to help you figure out the IR emitter stuff. Like I said, I've had it working in the past, and I'm going to have to get it working, again, myself, before October 20. That is the only (legal) inexpensive solution for you.