The DVR to be used on the FiOS system must be QAM and Cable Card compatible. It must also now support simulcrypt. There are different manufactures, but they must be compatible. You can't take a DVR that was made specifically for another provider and expect it to operate on FiOS. Many of the older cable card compatible devices will not support simulcrypt, so be careful if purchasing. I have a TiVO HD with a Verizon rented cable card connect directly to the FiOS coax and it works great for now, and has for over a year. But technology changes and how long the cablecard standard or the technology will stay the same, is anyone's guess. The TiVo requires a subscription to TiVO and you would not get the Verizon supported VOD, Guide, or Widgets. The TiVO subscription provides the channel guide. Verizon rents cable cards at $3.99 and they should work with any cable card compatible device that supports the full cable card standard including simulcrypt.
Yes you can use any DVR that supports and takes a CableCard.
Tivo's take cable cards
Moxi DVR's take cable cards
CETON Infinitv PC Tuner cards can take cable cards.
Without a Cable card you will not get all of your subscribed programming, so you will end up renting a cable card from Verizon which costs 3.99
The draw back to using your own DVR is that you won't take advantage of Verizon's Interactive Menu Guide, Video On Demand, or Widgets. You will use the provider that comes with or supports your equipment instead for those functions, so for example you will probably use netflix and amazon for Video on demand on TIVO.
The Cable Card from Verizon requires a field technician to come to your house and pair it with your DVR, and there is some mixed information at customer service about that. Some will tell you there is a charge, just smile and nod - there is no charge. some will tell you that they will mail it to you and you install it, just smile and nod and make sure you give them good contact information because a Technician will call you and ask when he can drop by to install it.
Now if you need the technician to wire a room that isn't already wired, then there may be a charge, or if he does additional work like that, but if he just installs the card, then there isn't a charge for that.
I like the MOXI personally but it has a heftier upfront cost, but then there isn't a monthly fee associated with it, the TIVO is a great unit and works SUPER well, is lower upfront cost but I think you have to choose from a subscription package to get the guide info, and the CETON is reasonably priced, but you are custom setting that up in a PC.
There are few others out there that take cable cards, but there are others out there.
Good detailed post. I have been lazy. I guess I couldn't remember Moxi and out of my $$ range. Ceton I have looked at but always a waiting list. Still $400 right. What worried me is when things start moving more to IP and the cablecard goes where? AT&T TV service IP and compressed to beat all, and TiVO does not work there does it?