Replace cable box with Tivo

It is my understanding that Tivo can replace the cable company's box with the use of two cable cards that must be provided by the cable company. Also I was told that the Tivo unit would provide HD viewing of those programs provided in HD by the cable company. Does anyone know if this is true? I appreciate any input anyone can provide.
strongly suggest you avoid 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 have TiVo HR10-250 and DirecTV Plus HD DVRs. The picture quality on both look absolutely splendid. I'm skeptical about Larry's universal pronouncement, thinking his experience might be particular.

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.
Geared, what model did you buy? I've been thinking about either adding tivo or doing what you did.
I got a really good deal on a Sony RDR-GXD455.
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.