You likely will be just fine. Most of the problems relate to the installation of Tivo, not the actual DVR experience once it gets going. After lurking on this site for months and reading all the scary posts about the installation I finally took the plunge and bought a Tivo HD fully expecting a disaster. But with trees blocking my DirecTV HD satellite I either go Comcast or never get HD. Luckily, I learned enough here to ask the right questions but it still wasn't easy. The patience of Jobe would help.
When I first called Comcast, I did as folks here say and I asked them to send me an experienced installer who had worked with Tivos before. I also asked for the installer to bring an M card, not two S cards, because folks here seem to think that's better.
Well, Comcast responded by sending out a sub-contractor tech on Monday who had never seen a Tivo in his life and basically wanted no part of this installation. He put in the M card, called in the codes, and it didn't work even though he said the "ping" had been done correctly. He then made an excuse about having other appointments and bolted.
From these forums, I knew to call Tivo, which then patienty went over some things with me on the screen that showed the card was working fine. The Tivo rep than called Comcast and we tried to get the card going in a three-way conversation with the cable company's repair folks. Two different Comcast technicians tried to get the card working and didn't. The last one concluded that that M card was bad and I needed to go to my local Comcast office and get another one (which others in these forums have done successfully). Well, I tried that, only to be told that the Comcast office in Rockville, Md. does not hand out M cards anymore and they would have to send out a rep. I again asked them to send out a Comcast person, not a subcontractor, who had experience with Tivos and M cards.
On Wednesday, Comcast sent me the real deal. In about five minutes he realized that one of the codes on the M card had been typed in incorrectly (I'm kicking myself because many folks here emphasize the need to double and triple check the codes that are called in by the technician to the main office. If even one of about 30 numbers or letters is wrong, it won't work). Anyway, the right numbers go in and boom, the Tivo comes up beautifully. All my channels, HBO too. No problems. And Tivo remains by far the best DVR on the planet.
I read a post here a while back that proved prophetic: the process is a bit of a roll of the dice. It depends on whether you get a technician who knows what he's doing. My first one did not, my second one did.
One other piece of advice on these forums that I should have followed: Set up the Tivo a couple days before the technician comes so you aren't doing the guided installation with a cable guy looking over your shoulder. Also, the Tivo will have time to download all the software upgrades. Hope this helps. Good luck.