strongly suggest you avoid Tivo...it noticeably degrades the picture quality. I switched to the Comcast HD dual channel box and the picture quality is stunning.
Walnut -- you are correct on all counts. The only thing to add is that by going to cable cards you lose two-way communication, so you can not get PPV.
Larryken -- very interesting, first time I have heard this, though I don't read AVS forum, so it may be old news. I bought the TiVo Series 3 the day it was released, that's how much I missed its UI compared to the Comcast box we got when we got our HD set. I was so happy to have TiVo back, I might have overlooked a difference in picture quality. Had it been truly noticeable, though, I think I would have noticed it immediately. Can you say more?
I had a very pleasant surprise this weekend. I bought my wife a new dvd recorder that had digital tuners as well as qam for digital cable. We have the most basic of cable packages that runs us $10 a month. I was amazed when I hooked up the cable to the recorder the tuner pulled in 30+ digital channels including abchd, cbshd, nbchd, our 3 local pbshd stations, and many more. The quality is superb and that $10 sure seems like a bargain now.
Replacing my RCN Cable box with a HD Tivo was one of the best tech decisions I've made.
Their is no noticeable difference in picture quality (I'm using a 50" Panasonic plasma, fed by a DVDO scaler).
To answer your question, yes, you get all of your cable provider's HD content through the Tivo, as long as it's an HD Tivo.
Advantages to this decision:
* Much better UI and menus
* More responsive remote (don't you hate how cable box remotes don't register commands and are slow?)
* Better DVR management
* Much less annoying advertising clogging up the program guide (can only see 4 channels per page on RCN's guide)
* Better engineered and more stable hardware (I had countless problems with various DVR boxes)
* Ability to easily drop a bigger hard drive in to increase DVR capacity
I would never, ever go back to a cable-provider DVR box. I can't think of a single advantage to using it, besides saving about $4 per month.