To the OP, I'm gonna jump in on this and give some feedback on my experiences so far as a relatively new user, and also pose a few questions/suggestions that I don't have answers to (yet):
I'm a sports junkie. Football particularly, and Saturday's specifically. I currently have 5 HDTVs in my house; 3 of them are in one room. It's a room built to showcase multiple live sporting events all at one time.
Up until last week, I was doing so by a complicated, cumbersome, system of wires and slingboxes, with one local Comcast DVR, one sling catcher, 3 "independent" cable inputs (no "splitters"), and one of their stupid standard def "Digital Adapters" (the "transfer to digital" really made things more difficult/cumbersome, but I won't bore you with the details).
Last week I finally "took the plunge" into the HTPC world. I bought a quad-core PC running Windows 7, an AMD ATI Graphics Card, 16 gigs of RAM and 4 TB of internal hard drive space. I installed a Ceton InfiniTV cable card, which as you know can tune and record 4 channels at once.
First, the positives:
1) Outside of problems with my Norton Firewall, setup was relatively painless, and integration with WMC is fantastic.
2) Everything that is slow and annoying about one of those $20-a-month cable boxes is fast and seemless in WMC.
3)Having four tuners and one "central recording location" is nice, and paying the cable company $6-$7 a month for one M-Card instead of $19-$20 a month for one of their stupid boxes is satisfying.
4) I already owned an XBox 360, located upstairs on my "Home Theater" set-up. Integration as a WMC Extender was likewise painless, and now ALL of my digital music on my hard-drive is readily available upstairs on my "best stereo". Very cool. And convenient.
5) My cable company (Comcast, here in Southwestern PA) doesn't appear to be flagging much content, including live sports over cable network channels, as Copy Once. Great news if this is true for you as well.
Now, some negatives:
A) I have 3 TV's side-by-side. Now, because I read AVS, I knew before I purchased/installed that this supposedly wouldn't work, and so far I can confirm that I don't see/haven't found a way to make it work, but despite having 3 screens right next to each other, 3 unique outputs from my graphics card (1 HDMI, 1 DVI, and 1 VGA), and 3+ seperate TV tuners available, even though I can extend my desktop to multiple screens I cannot run multiple instances of WMC. If I could? That would be fantastic. But I don't believe it's possible, and even though I knew that was the case before I bought it, I still find it to be disappointing.
B) We also have a laptop running Windows Vista Home Premier, which means it also has WMC installed. Although I haven't yet gotten it fully integrated (I hope to make progress with that tonight, I think I need to enable some sort of "network sharing" of the folders on the HTPC first) yet, it appears that I will not be able to take over a tuner "live" on that laptop. I suppose a workaround would be to start a recording and then have that laptop play the file while the recording is being made, but this is likewise disappointing. I had assumed that other WMC-capable PCs (be it laptops or netbooks) would be able to grab a tuner whenever. That doesn't appear to be the case.
C) "Remote Potato" (which I'm currently trying to get to work) should allow mobile devices or other PCs without WMC installed to access HTPC content, but again, they can't get access to a Live tuner. You have to start a recording and then begin playback.
D) Xbox 360's are cool, and I was impressed with all of it's functionality when I paired it to the HTPC, but I already own one. They're loud, they draw a lot of power, and at $300, the most bare-bones "to be used as WMC Extender only" costs about as much as a half-decent Netbook that would be a great extender if only for limitations discussed in "B" above.
So what can we do for "extenders" that don't cost an arm-and-a-leg, and will be able to grab live-tuners and have some useful functionality? Right now I'm contemplating adding one of the SiliconDust products. If a mobile apple device can access a tuner live (without something like Remote Potato), and your iPad, iPhone, or iPod Touch has HDMI out, then why can't any of these devices (particularly iPod Touch's) function as "extenders" to a TV? Additionally, if I'm reading their website correctly, I think laptops/netbooks might also be able to grab a Live tuner, whereas they don't appear to be able to do so with my currently-installed Ceton InfiniTV card.
Just some feedback for you, both positive and negative, about my experiences so far, and some thoughts/ideas that I haven't had a chance to work through yet. I hope to have Remote Potato and the laptop's WMC instance functioning tonight, and if I find anything surprising I'll share my findings.