I would love to say HTPC alone, however I've had to add a standalone Blu-ray player to my home theater because the software players do not get updates as fast as the standalone players do. Obviously this is about which has a better market and what product line gets catered to.
As an avid Boxee user I can see the appeal of ditching cable/satellite altogether. It's certainly possible to get pretty much everything you need with a decent machine and a mix of Netflix, iTunes and Hulu.
The thing that will keep me subscribed to cable is that Comcast carries all the games for the only team I care about (Portland Trailblazers). Once the NBA get's their live streaming shit figured out me and Comcast are splitsville.
I have a ghetto shuttle that I put together a couple of years back, with networking I can grab any media, on any computer in my house, and put it on my TV. As well as record shows and watch them from any computer.
i have an HD cable box, HDTV w/ ATSC tuner & a 17" Intel iMac w/ 1.25 TB of HDDs for iTunes music & DVD rips, attached on my main HT set-up. i stream over my WiFi network from the iMac to my MacBook & connect to my BR TV. OTA, Online, cable & a server, i'm mostly good to go.
I use XBMC for Windows, combined with tvrss.net and Vuze/Azureus, it pretty much beats any PVR. I've had Tivos before, and my HTPC also has Vista Media Center and a HDTV tuner.
Since I'm paying for the TV programming anyways, I don't feel like what I do is illegal. And having the HTPC gives me the ability to *easily* view anything that one can view on a PC on my big TV screen without the hassle of entering text through a remote control or limits of set-top-box software/processors.
By the way, in case the 3 HTPCs thing looks extravagent, two of them I got in closing down sales at Compusa and the third was a 10 year old box I upgraded for $200 with a new HDMI motherboard.
I've got 3 HTPCs hooked up to big screens so I guess my vote is obvious. But I also have a Dish HD DVR and one of the HTPCs has a Blu-Ray drive in it, so I'm far from getting everything online (yet). There's a lot of content online but not much of it is true HD and almost none of it has 5.1 sound attached to it (yet), plus there are still big gaps in the content you can find online.
I like to consider myself more 'cutting edge' than most. I built a dedicated MythTV (Mythdora 5) machine and it does it all and more. No way would I give in for any Windows Media center crap.