You may have this resolved by now but figured I would add what I know as of mid-October.I am also a CV customer in NY and have used media center for years, but am only just considering trying CableCARD. Based on the FAQ posted here:
http://thegreenbutton.com/blogs/windows_media_center_team_blog/archive/2009/10/05/393171.aspx
I decided to call into CV support and check it out and this is what I found:
I gave the exact setup described in the above FAQ (an external ATI digital tuner) as my desired configuration
Cablevision here in NY confirmed that by going to CableCARD today I would loose "several" HD channels. (they mentioned that some HBO channels would be gone for example). Although I did not get a precise explanation the tech told simply that "some HD channels just do not work on a CableCARD"... hmmm.
In addition, I would loose PPV via remote and the channel guide (which I already knew about). They also mentioned lack of SDV support but it was clear the person was reading from a script. The person did not mention a tuning adapter until I specifically asked about it but then said "yes, a tuning adapter is available free of charge for our CableCARD customers". The tech specifically told me that I needed a CableCARD-ready television for this all to work as they assume that this is how you are going to do it... The tech also then mentioned a "single stream" and "multiple stream" version of the product (I assume they were speaking of the TA?) but I realize now that this part is not clear - at least for me at the moment. I googled Cisco tuning adapters and do not see anything in the specification so perhaps it is the CableCARD itself...
I then got higher level support on the phone for more / better information. They confirmed that CV customers were using currently using CableCARD AND the tuning adapter for Tivo setups. No surprise, he was not sure if this would work on a Windows 7 PC and could not commit that it WOULD work but he said there should not be an issue with getting a field tech to come out and attempt installation and activation of a CableCARD and TA for a Media Center setup.However, he was also sketchy about confirming that I would then receive all channels in my currently subscribed line-up - even with the TA. ... double hmmmm....
Reading other forum notes on missing content I've seen at least a few others needing to have the cable operator re-check authorized channels - apparently, they sometimes overlook a few authorized channels on the initial CableCARD setup. (No idea WHY this would happen... but apparently it does) After authorization you may get the missing channels.
So you are probably looking at getting a tuning adapter from CV (they supply for free) and hooking that up and you may also then be looking at re-authorizing your CableCARD with CV to get any currently missed programming.
Overall this still seems way too goofy for the average user but I think most would agree with that. The nonsense that cable providers are dishing out to customers is stupid and I do not trust them. After all this time getting into CableCARD still means navigating a lot of nonsense to get LESS than what you pay for with ADDITIONAL expense and complexity of the extra equipment.And what's up with the planet-of-the-ape-sized tuning adapter??? Jeesh... My concept was to use a low-power small form factor HTPC case running WMC 7 and I specifically did not want a STB hanging off of it. Now I need an external CableCARD tuner AND a Tuning Adapter to get less functionality and arguably a more complicated setup.
I'd also be curious as to what happens on a service call when the setup stops working... what if you only have CableCARD on your Media Center and it's broken? The only thing you can probably confirm is if other set-top boxes in the house (if any) are still working... if they are, then how will CV or others support you? My guess is that they will shrug and say this your configuration is not supported and leave you hanging.
This stuff is a LONG way off from consumer level.